diff --git chrome/browser/ui/browser_command_controller.cc chrome/browser/ui/browser_command_controller.cc
index 85dc58159a58a..9b582e691f6d8 100644
--- chrome/browser/ui/browser_command_controller.cc
+++ chrome/browser/ui/browser_command_controller.cc
@@ -402,6 +402,7 @@ bool BrowserCommandController::ExecuteCommandWithDisposition(
   // choose to not implement CommandUpdaterDelegate inside this class and
   // therefore command_updater_ doesn't have the delegate set).
   if (!SupportsCommand(id) || !IsCommandEnabled(id)) {
+    LOG(WARNING) << "Invalid/disabled command " << id;
     return false;
   }
 
@@ -418,6 +419,13 @@ bool BrowserCommandController::ExecuteCommandWithDisposition(
   DCHECK(command_updater_.IsCommandEnabled(id))
       << "Invalid/disabled command " << id;
 
+#if BUILDFLAG(ENABLE_CEF)
+  if (browser_->cef_delegate() &&
+      browser_->cef_delegate()->HandleCommand(id, disposition)) {
+    return true;
+  }
+#endif
+
   // The order of commands in this switch statement must match the function
   // declaration order in browser.h!
   switch (id) {
@@ -1152,11 +1160,13 @@ void BrowserCommandController::TabRestoreServiceLoaded(
 // BrowserCommandController, private:
 
 bool BrowserCommandController::IsShowingMainUI() {
-  return browser_->SupportsWindowFeature(Browser::FEATURE_TABSTRIP);
+  return browser_->SupportsWindowFeature(Browser::FEATURE_TABSTRIP) ||
+         browser_->toolbar_overridden();
 }
 
 bool BrowserCommandController::IsShowingLocationBar() {
-  return browser_->SupportsWindowFeature(Browser::FEATURE_LOCATIONBAR);
+  return browser_->SupportsWindowFeature(Browser::FEATURE_LOCATIONBAR) ||
+         browser_->toolbar_overridden();
 }
 
 bool BrowserCommandController::IsWebAppOrCustomTab() const {
diff --git chrome/browser/ui/toolbar/app_menu_model.cc chrome/browser/ui/toolbar/app_menu_model.cc
index d2b2a605cbba5..afaf26c26a6db 100644
--- chrome/browser/ui/toolbar/app_menu_model.cc
+++ chrome/browser/ui/toolbar/app_menu_model.cc
@@ -590,6 +590,57 @@ SaveAndShareSubMenuModel::SaveAndShareSubMenuModel(
   }
 }
 
+#if BUILDFLAG(ENABLE_CEF)
+using IsVisibleCallback = base::RepeatingCallback<bool(int)>;
+
+void FilterMenuModel(ui::SimpleMenuModel* model,
+                     const IsVisibleCallback& is_visible) {
+  absl::optional<size_t> last_separator;
+  size_t visible_ct = 0;
+  for (size_t i = 0; i < model->GetItemCount(); ++i) {
+    const auto type = model->GetTypeAt(i);
+    if (type == ui::MenuModel::TYPE_SEPARATOR) {
+      if (last_separator) {
+        // Remove multiple separators in a row. Prefer to remove a NORMAL
+        // separator if possible (as compared to zoom/edit controls which use
+        // UPPER/LOWER separators).
+        if (model->GetSeparatorTypeAt(*last_separator) ==
+            ui::NORMAL_SEPARATOR) {
+          model->RemoveItemAt(*last_separator);
+          i--;
+          last_separator = i;
+        } else {
+          model->RemoveItemAt(i);
+          i--;
+        }
+      } else if (visible_ct == 0) {
+        // Remove leading separator.
+        model->RemoveItemAt(i);
+        i--;
+      } else {
+        last_separator = i;
+      }
+      visible_ct = 0;
+    } else if (is_visible.Run(model->GetCommandIdAt(i))) {
+      last_separator = absl::nullopt;
+      visible_ct++;
+
+      if (type == ui::MenuModel::TYPE_SUBMENU) {
+        // Filter sub-menu.
+        auto sub_model =
+            static_cast<ui::SimpleMenuModel*>(model->GetSubmenuModelAt(i));
+        FilterMenuModel(sub_model, is_visible);
+      }
+    }
+  }
+
+  if (last_separator) {
+    // Remove trailing separator.
+    model->RemoveItemAt(*last_separator);
+  }
+}
+#endif  // BUILDFLAG(ENABLE_CEF)
+
 }  // namespace
 
 ////////////////////////////////////////////////////////////////////////////////
@@ -1382,7 +1433,7 @@ bool AppMenuModel::IsCommandIdChecked(int command_id) const {
   return false;
 }
 
-bool AppMenuModel::IsCommandIdEnabled(int command_id) const {
+bool AppMenuModel::IsCommandIdEnabledInternal(int command_id) const {
   GlobalError* error =
       GlobalErrorServiceFactory::GetForProfile(browser_->profile())
           ->GetGlobalErrorByMenuItemCommandID(command_id);
@@ -1397,6 +1448,30 @@ bool AppMenuModel::IsCommandIdEnabled(int command_id) const {
   }
 }
 
+bool AppMenuModel::IsCommandIdEnabled(int command_id) const {
+  if (!IsCommandIdEnabledInternal(command_id)) {
+    return false;
+  }
+
+#if BUILDFLAG(ENABLE_CEF)
+  if (browser_->cef_delegate()) {
+    return browser_->cef_delegate()->IsAppMenuItemEnabled(command_id);
+  }
+#endif
+
+  return true;
+}
+
+bool AppMenuModel::IsCommandIdVisible(int command_id) const {
+#if BUILDFLAG(ENABLE_CEF)
+  if (browser_->cef_delegate()) {
+    return browser_->cef_delegate()->IsAppMenuItemVisible(command_id);
+  }
+#endif
+
+  return true;
+}
+
 bool AppMenuModel::IsCommandIdAlerted(int command_id) const {
   if ((command_id == IDC_RECENT_TABS_MENU) ||
       (command_id == AppMenuModel::kMinRecentTabsCommandId)) {
@@ -1566,11 +1641,15 @@ void AppMenuModel::Build() {
                                        kDefaultIconSize));
   }
 
-  AddSeparator(features::IsChromeRefresh2023() ? ui::NORMAL_SEPARATOR
-                                               : ui::LOWER_SEPARATOR);
-  CreateZoomMenu();
-  AddSeparator(features::IsChromeRefresh2023() ? ui::NORMAL_SEPARATOR
-                                               : ui::UPPER_SEPARATOR);
+  if (IsCommandIdVisible(IDC_ZOOM_MENU)) {
+    AddSeparator(features::IsChromeRefresh2023() ? ui::NORMAL_SEPARATOR
+                                                 : ui::LOWER_SEPARATOR);
+    CreateZoomMenu();
+    AddSeparator(features::IsChromeRefresh2023() ? ui::NORMAL_SEPARATOR
+                                                 : ui::UPPER_SEPARATOR);
+  } else {
+    AddSeparator(ui::NORMAL_SEPARATOR);
+  }
 
   AddItemWithStringId(IDC_PRINT, IDS_PRINT);
 
@@ -1651,9 +1730,13 @@ void AppMenuModel::Build() {
                          kMoreToolsMenuItem);
 
   if (!features::IsChromeRefresh2023()) {
-    AddSeparator(ui::LOWER_SEPARATOR);
-    CreateCutCopyPasteMenu();
-    AddSeparator(ui::UPPER_SEPARATOR);
+    if (IsCommandIdVisible(IDC_EDIT_MENU)) {
+      AddSeparator(ui::LOWER_SEPARATOR);
+      CreateCutCopyPasteMenu();
+      AddSeparator(ui::UPPER_SEPARATOR);
+    } else {
+      AddSeparator(ui::NORMAL_SEPARATOR);
+    }
   }
 
   if (!features::IsChromeRefresh2023()) {
@@ -1739,6 +1822,11 @@ void AppMenuModel::Build() {
     SetCommandIcon(this, IDC_EXIT, kExitMenuIcon);
   }
 
+#if BUILDFLAG(ENABLE_CEF)
+  FilterMenuModel(this, base::BindRepeating(&AppMenuModel::IsCommandIdVisible,
+                                            base::Unretained(this)));
+#endif
+
   uma_action_recorded_ = false;
 }
 
diff --git chrome/browser/ui/toolbar/app_menu_model.h chrome/browser/ui/toolbar/app_menu_model.h
index f06cf1bf08ba4..4e89b522715fc 100644
--- chrome/browser/ui/toolbar/app_menu_model.h
+++ chrome/browser/ui/toolbar/app_menu_model.h
@@ -204,6 +204,7 @@ class AppMenuModel : public ui::SimpleMenuModel,
   void ExecuteCommand(int command_id, int event_flags) override;
   bool IsCommandIdChecked(int command_id) const override;
   bool IsCommandIdEnabled(int command_id) const override;
+  bool IsCommandIdVisible(int command_id) const override;
   bool IsCommandIdAlerted(int command_id) const override;
   bool GetAcceleratorForCommandId(int command_id,
                                   ui::Accelerator* accelerator) const override;
@@ -236,6 +237,8 @@ class AppMenuModel : public ui::SimpleMenuModel,
   // took to select the command.
   void LogMenuMetrics(int command_id);
 
+  bool IsCommandIdEnabledInternal(int command_id) const;
+
  private:
   // Adds actionable global error menu items to the menu.
   // Examples: Extension permissions and sign in errors.
diff --git chrome/browser/ui/views/find_bar_host.cc chrome/browser/ui/views/find_bar_host.cc
index 59024587ef6b7..0c30aa71768cf 100644
--- chrome/browser/ui/views/find_bar_host.cc
+++ chrome/browser/ui/views/find_bar_host.cc
@@ -412,6 +412,12 @@ void FindBarHost::GetWidgetBounds(gfx::Rect* bounds) {
   // The BrowserView does Layout for the components that we care about
   // positioning relative to, so we ask it to tell us where we should go.
   *bounds = browser_view()->GetFindBarBoundingBox();
+
+#if BUILDFLAG(ENABLE_CEF)
+  if (browser_view()->browser() && browser_view()->browser()->cef_delegate()) {
+    browser_view()->browser()->cef_delegate()->UpdateFindBarBoundingBox(bounds);
+  }
+#endif
 }
 
 void FindBarHost::RegisterAccelerators() {
diff --git chrome/browser/ui/views/frame/browser_frame.cc chrome/browser/ui/views/frame/browser_frame.cc
index bb4b3821bcfda..4014f61a7057f 100644
--- chrome/browser/ui/views/frame/browser_frame.cc
+++ chrome/browser/ui/views/frame/browser_frame.cc
@@ -114,15 +114,23 @@ ui::ColorProviderKey::SchemeVariant GetSchemeVariant(
 ////////////////////////////////////////////////////////////////////////////////
 // BrowserFrame, public:
 
+BrowserFrame::BrowserFrame() : BrowserFrame(nullptr) {}
+
 BrowserFrame::BrowserFrame(BrowserView* browser_view)
     : native_browser_frame_(nullptr),
       root_view_(nullptr),
       browser_frame_view_(nullptr),
-      browser_view_(browser_view) {
-  browser_view_->set_frame(this);
+      browser_view_(nullptr) {
   set_is_secondary_widget(false);
   // Don't focus anything on creation, selecting a tab will set the focus.
   set_focus_on_creation(false);
+  if (browser_view)
+    InitBrowserView(browser_view);
+}
+
+void BrowserFrame::InitBrowserView(BrowserView* browser_view) {
+  browser_view_ = browser_view;
+  browser_view_->set_frame(this);
 }
 
 BrowserFrame::~BrowserFrame() {}
@@ -228,10 +236,20 @@ void BrowserFrame::LayoutWebAppWindowTitle(
 }
 
 int BrowserFrame::GetTopInset() const {
+  if (!browser_frame_view_) {
+    // With CEF the browser may already be part of a larger Views layout. Zero
+    // out the adjustment in BrowserView::GetTopInsetInBrowserView() so that
+    // the browser isn't shifted to the top of the window.
+    return browser_view_->y();
+  }
   return browser_frame_view_->GetTopInset(false);
 }
 
 void BrowserFrame::UpdateThrobber(bool running) {
+  if (!browser_frame_view_) {
+    // Not supported with CEF Views-hosted DevTools windows.
+    return;
+  }
   browser_frame_view_->UpdateThrobber(running);
 }
 
@@ -240,6 +258,8 @@ BrowserNonClientFrameView* BrowserFrame::GetFrameView() const {
 }
 
 bool BrowserFrame::UseCustomFrame() const {
+  if (!native_browser_frame_)
+    return true;
   return native_browser_frame_->UseCustomFrame();
 }
 
@@ -253,20 +273,30 @@ bool BrowserFrame::ShouldDrawFrameHeader() const {
 
 void BrowserFrame::GetWindowPlacement(gfx::Rect* bounds,
                                       ui::WindowShowState* show_state) const {
+  if (!native_browser_frame_) {
+    *show_state = ui::SHOW_STATE_DEFAULT;
+    return;
+  }
   return native_browser_frame_->GetWindowPlacement(bounds, show_state);
 }
 
 content::KeyboardEventProcessingResult BrowserFrame::PreHandleKeyboardEvent(
     const content::NativeWebKeyboardEvent& event) {
+  if (!native_browser_frame_)
+    return content::KeyboardEventProcessingResult::NOT_HANDLED;
   return native_browser_frame_->PreHandleKeyboardEvent(event);
 }
 
 bool BrowserFrame::HandleKeyboardEvent(
     const content::NativeWebKeyboardEvent& event) {
+  if (!native_browser_frame_)
+    return false;
   return native_browser_frame_->HandleKeyboardEvent(event);
 }
 
 void BrowserFrame::OnBrowserViewInitViewsComplete() {
+  if (!browser_frame_view_)
+    return;
   browser_frame_view_->OnBrowserViewInitViewsComplete();
 }
 
@@ -367,6 +397,8 @@ ui::ColorProviderKey::ThemeInitializerSupplier* BrowserFrame::GetCustomTheme()
 }
 
 void BrowserFrame::OnNativeWidgetWorkspaceChanged() {
+  if (!browser_view_)
+    return;
   chrome::SaveWindowWorkspace(browser_view_->browser(), GetWorkspace());
   chrome::SaveWindowVisibleOnAllWorkspaces(browser_view_->browser(),
                                            IsVisibleOnAllWorkspaces());
@@ -478,6 +510,8 @@ void BrowserFrame::OnNativeThemeUpdated(ui::NativeTheme* observed_theme) {
 
 ui::ColorProviderKey BrowserFrame::GetColorProviderKey() const {
   auto key = Widget::GetColorProviderKey();
+  if (!browser_view_)
+    return key;
 
   key.app_controller = browser_view_->browser()->app_controller();
 
@@ -632,5 +666,8 @@ bool BrowserFrame::RegenerateFrameOnThemeChange(
 }
 
 bool BrowserFrame::IsIncognitoBrowser() const {
+  if (!browser_view_) {
+    return true;
+  }
   return browser_view_->browser()->profile()->IsIncognitoProfile();
 }
diff --git chrome/browser/ui/views/frame/browser_frame.h chrome/browser/ui/views/frame/browser_frame.h
index 0c231b6ac5b01..6b5af98e18e42 100644
--- chrome/browser/ui/views/frame/browser_frame.h
+++ chrome/browser/ui/views/frame/browser_frame.h
@@ -61,7 +61,9 @@ enum class TabDragKind {
 // This is a virtual interface that allows system specific browser frames.
 class BrowserFrame : public views::Widget, public views::ContextMenuController {
  public:
+  BrowserFrame();
   explicit BrowserFrame(BrowserView* browser_view);
+  void InitBrowserView(BrowserView* browser_view);
 
   BrowserFrame(const BrowserFrame&) = delete;
   BrowserFrame& operator=(const BrowserFrame&) = delete;
diff --git chrome/browser/ui/views/frame/browser_view.cc chrome/browser/ui/views/frame/browser_view.cc
index 41376bb2d8af1..fa9ede3614aca 100644
--- chrome/browser/ui/views/frame/browser_view.cc
+++ chrome/browser/ui/views/frame/browser_view.cc
@@ -343,11 +343,10 @@ using content::NativeWebKeyboardEvent;
 using content::WebContents;
 using web_modal::WebContentsModalDialogHost;
 
-namespace {
+// static
+const char BrowserView::kBrowserViewKey[] = "__BROWSER_VIEW__";
 
-// The name of a key to store on the window handle so that other code can
-// locate this object using just the handle.
-const char* const kBrowserViewKey = "__BROWSER_VIEW__";
+namespace {
 
 #if BUILDFLAG(IS_CHROMEOS_ASH)
 // UMA histograms that record animation smoothness for tab loading animation.
@@ -843,12 +842,23 @@ class BrowserView::AccessibilityModeObserver : public ui::AXModeObserver {
 ///////////////////////////////////////////////////////////////////////////////
 // BrowserView, public:
 
+BrowserView::BrowserView() : BrowserView(nullptr) {}
+
 BrowserView::BrowserView(std::unique_ptr<Browser> browser)
     : views::ClientView(nullptr, nullptr),
-      browser_(std::move(browser)),
       accessibility_mode_observer_(
-          std::make_unique<AccessibilityModeObserver>(this)),
-      browser_actions_(*browser_) {
+          std::make_unique<AccessibilityModeObserver>(this)) {
+  if (browser)
+    InitBrowser(std::move(browser));
+}
+
+void BrowserView::InitBrowser(std::unique_ptr<Browser> browser) {
+  DCHECK(!browser_);
+  browser_ = std::move(browser);
+
+  browser_actions_ = std::make_unique<BrowserActions>(*browser_);
+  immersive_mode_controller_ = chrome::CreateImmersiveModeController(this);
+
   SetShowIcon(
       ::ShouldShowWindowIcon(browser_.get(), AppUsesWindowControlsOverlay()));
 
@@ -897,7 +907,6 @@ BrowserView::BrowserView(std::unique_ptr<Browser> browser)
   }
 
   browser_->tab_strip_model()->AddObserver(this);
-  immersive_mode_controller_ = chrome::CreateImmersiveModeController(this);
 
   // Top container holds tab strip region and toolbar and lives at the front of
   // the view hierarchy.
@@ -956,8 +965,15 @@ BrowserView::BrowserView(std::unique_ptr<Browser> browser)
   contents_container->SetLayoutManager(std::make_unique<ContentsLayoutManager>(
       devtools_web_view_, contents_web_view_));
 
-  toolbar_ = top_container_->AddChildView(
-      std::make_unique<ToolbarView>(browser_.get(), this));
+  toolbar_ = OverrideCreateToolbar();
+  if (!toolbar_) {
+    toolbar_ = new ToolbarView(browser_.get(), this, absl::nullopt);
+  } else {
+    browser_->set_toolbar_overridden(true);
+    // Update state that depends on the above flag.
+    browser_->command_controller()->FullscreenStateChanged();
+  }
+  top_container_->AddChildView(base::WrapUnique(toolbar_.get()));
 
   contents_separator_ =
       top_container_->AddChildView(std::make_unique<ContentsSeparator>());
@@ -1031,7 +1047,9 @@ BrowserView::~BrowserView() {
 
   // All the tabs should have been destroyed already. If we were closed by the
   // OS with some tabs than the NativeBrowserFrame should have destroyed them.
+  if (browser_) {
   DCHECK_EQ(0, browser_->tab_strip_model()->count());
+  }
 
   // Stop the animation timer explicitly here to avoid running it in a nested
   // message loop, which may run by Browser destructor.
@@ -1045,12 +1063,14 @@ BrowserView::~BrowserView() {
   // child views and it is an observer for avatar toolbar button if any.
   autofill_bubble_handler_.reset();
 
+  if (browser_) {
   auto* global_registry =
       extensions::ExtensionCommandsGlobalRegistry::Get(browser_->profile());
   if (global_registry->registry_for_active_window() ==
       extension_keybinding_registry_.get()) {
     global_registry->set_registry_for_active_window(nullptr);
   }
+  }
 
   // The TabStrip attaches a listener to the model. Make sure we shut down the
   // TabStrip first so that it can cleanly remove the listener.
@@ -1068,7 +1088,9 @@ BrowserView::~BrowserView() {
 
   // `SidePanelUI::RemoveSidePanelUIForBrowser()` deletes the
   // SidePanelCoordinator.
+  if (browser()) {
   SidePanelUI::RemoveSidePanelUIForBrowser(browser());
+  }
 }
 
 // static
@@ -1939,9 +1961,14 @@ void BrowserView::OnExclusiveAccessUserInput() {
 
 bool BrowserView::ShouldHideUIForFullscreen() const {
   // Immersive mode needs UI for the slide-down top panel.
-  if (immersive_mode_controller_->IsEnabled())
+  // Avoid callback into |immersive_mode_controller_| during construction.
+  // See CEF issue #3527.
+  if (immersive_mode_controller_ &&
+      immersive_mode_controller_->IsEnabled())
     return false;
 
+  if (!frame_->GetFrameView())
+    return false;
   return frame_->GetFrameView()->ShouldHideTopUIForFullscreen();
 }
 
@@ -2956,7 +2983,8 @@ DownloadShelf* BrowserView::GetDownloadShelf() {
 }
 
 DownloadBubbleUIController* BrowserView::GetDownloadBubbleUIController() {
-  DCHECK(toolbar_button_provider_);
+  if (!toolbar_button_provider_)
+    return nullptr;
   if (auto* download_button = toolbar_button_provider_->GetDownloadButton())
     return download_button->bubble_controller();
   return nullptr;
@@ -3490,7 +3518,8 @@ void BrowserView::ReparentTopContainerForEndOfImmersive() {
   if (top_container()->parent() == this)
     return;
 
-  overlay_view_->SetVisible(false);
+  if (overlay_view_)
+    overlay_view_->SetVisible(false);
   top_container()->DestroyLayer();
   AddChildViewAt(top_container(), 0);
   EnsureFocusOrder();
@@ -3948,11 +3977,38 @@ void BrowserView::GetAccessiblePanes(std::vector<views::View*>* panes) {
 bool BrowserView::ShouldDescendIntoChildForEventHandling(
     gfx::NativeView child,
     const gfx::Point& location) {
+#if BUILDFLAG(ENABLE_CEF)
+  const bool frameless_pip =
+      GetIsPictureInPictureType() &&
+      !browser_->SupportsWindowFeature(Browser::FEATURE_TITLEBAR);
+  if (frameless_pip) {
+    if (auto frame_view = frame()->GetFrameView()) {
+      int result = frame_view->NonClientHitTest(location);
+      if (result == HTTOP || result == HTTOPLEFT || result == HTTOPRIGHT) {
+        // Allow resize from the top of a frameless window.
+        return false;
+      }
+    }
+  }
+#endif
+
+  absl::optional<SkRegion> draggable_region;
+
   // Window for PWAs with window-controls-overlay display override should claim
   // mouse events that fall within the draggable region.
   web_app::AppBrowserController* controller = browser()->app_controller();
-  if (AreDraggableRegionsEnabled() && controller &&
-      controller->draggable_region().has_value()) {
+  if (AreDraggableRegionsEnabled() && controller) {
+    draggable_region = controller->draggable_region();
+  }
+
+#if BUILDFLAG(ENABLE_CEF)
+  // Match logic in PictureInPictureBrowserFrameView::NonClientHitTest.
+  if (!draggable_region.has_value() && frameless_pip) {
+    draggable_region = browser_->cef_delegate()->GetDraggableRegion();
+  }
+#endif
+
+  if (draggable_region.has_value()) {
     // Draggable regions are defined relative to the web contents.
     gfx::Point point_in_contents_web_view_coords(location);
     views::View::ConvertPointToTarget(GetWidget()->GetRootView(),
@@ -3961,7 +4017,7 @@ bool BrowserView::ShouldDescendIntoChildForEventHandling(
 
     // Draggable regions should be ignored for clicks into any browser view's
     // owned widgets, for example alerts, permission prompts or find bar.
-    return !controller->draggable_region()->contains(
+    return !draggable_region->contains(
                point_in_contents_web_view_coords.x(),
                point_in_contents_web_view_coords.y()) ||
            WidgetOwnedByAnchorContainsPoint(point_in_contents_web_view_coords);
@@ -4069,8 +4125,10 @@ void BrowserView::Layout() {
 
   // TODO(jamescook): Why was this in the middle of layout code?
   toolbar_->location_bar()->omnibox_view()->SetFocusBehavior(
-      IsToolbarVisible() ? FocusBehavior::ALWAYS : FocusBehavior::NEVER);
-  frame()->GetFrameView()->UpdateMinimumSize();
+      (IsToolbarVisible() || browser_->toolbar_overridden()) ?
+          FocusBehavior::ALWAYS : FocusBehavior::NEVER);
+  if (frame()->GetFrameView())
+    frame()->GetFrameView()->UpdateMinimumSize();
 
 #if BUILDFLAG(IS_CHROMEOS_ASH)
   // In chromeOS ash we round the bottom two corners of the browser frame by
@@ -4148,6 +4206,11 @@ void BrowserView::AddedToWidget() {
   SetThemeProfileForWindow(GetNativeWindow(), browser_->profile());
 #endif
 
+  // This browser view may already have a custom button provider set (e.g the
+  // hosted app frame).
+  if (!toolbar_button_provider_)
+    SetToolbarButtonProvider(toolbar_);
+
   toolbar_->Init();
 
   // TODO(pbos): Investigate whether the side panels should be creatable when
@@ -4196,13 +4259,9 @@ void BrowserView::AddedToWidget() {
 
   EnsureFocusOrder();
 
-  // This browser view may already have a custom button provider set (e.g the
-  // hosted app frame).
-  if (!toolbar_button_provider_)
-    SetToolbarButtonProvider(toolbar_);
-
   frame_->OnBrowserViewInitViewsComplete();
-  frame_->GetFrameView()->UpdateMinimumSize();
+  if (frame_->GetFrameView())
+    frame_->GetFrameView()->UpdateMinimumSize();
   using_native_frame_ = frame_->ShouldUseNativeFrame();
 
   MaybeInitializeWebUITabStrip();
@@ -4614,7 +4673,8 @@ void BrowserView::ProcessFullscreen(bool fullscreen,
   // Undo our anti-jankiness hacks and force a re-layout.
   in_process_fullscreen_ = false;
   ToolbarSizeChanged(false);
-  frame_->GetFrameView()->OnFullscreenStateChanged();
+  if (frame_->GetFrameView())
+    frame_->GetFrameView()->OnFullscreenStateChanged();
 }
 
 bool BrowserView::ShouldUseImmersiveFullscreenForUrl(const GURL& url) const {
@@ -5003,6 +5063,8 @@ Profile* BrowserView::GetProfile() {
 }
 
 void BrowserView::UpdateUIForTabFullscreen() {
+  if (!frame_->GetFrameView())
+    return;
   frame()->GetFrameView()->UpdateFullscreenTopUI();
 }
 
@@ -5025,6 +5087,8 @@ void BrowserView::HideDownloadShelf() {
 }
 
 bool BrowserView::CanUserExitFullscreen() const {
+  if (!frame_->GetFrameView())
+    return true;
   return frame_->GetFrameView()->CanUserExitFullscreen();
 }
 
diff --git chrome/browser/ui/views/frame/browser_view.h chrome/browser/ui/views/frame/browser_view.h
index f6251860d8bd3..9756332121fd8 100644
--- chrome/browser/ui/views/frame/browser_view.h
+++ chrome/browser/ui/views/frame/browser_view.h
@@ -140,11 +140,16 @@ class BrowserView : public BrowserWindow,
     kUnknown
   };
 
+  BrowserView();
   explicit BrowserView(std::unique_ptr<Browser> browser);
+  void InitBrowser(std::unique_ptr<Browser> browser);
   BrowserView(const BrowserView&) = delete;
   BrowserView& operator=(const BrowserView&) = delete;
   ~BrowserView() override;
 
+  // Key used to bind BrowserView to the Widget with which it is associated.
+  static const char kBrowserViewKey[];
+
   void set_frame(BrowserFrame* frame) {
     frame_ = frame;
     paint_as_active_subscription_ =
@@ -377,7 +382,7 @@ class BrowserView : public BrowserWindow,
   }
 
   actions::ActionItem* root_action_item() const {
-    return browser_actions_.root_action_item();
+    return browser_actions_->root_action_item();
   }
 
   // Returns true if the view has been initialized.
@@ -822,6 +827,9 @@ class BrowserView : public BrowserWindow,
   // TopContainerBackground::PaintThemeCustomImage for details.
   gfx::Point GetThemeOffsetFromBrowserView() const;
 
+ protected:
+  virtual ToolbarView* OverrideCreateToolbar() { return nullptr; }
+
  private:
   // Do not friend BrowserViewLayout. Use the BrowserViewLayoutDelegate
   // interface to keep these two classes decoupled and testable.
@@ -1255,7 +1263,7 @@ class BrowserView : public BrowserWindow,
 
   // `browser_actions_` creates the root browser level action along with child
   // actions.
-  const BrowserActions browser_actions_;
+  std::unique_ptr<BrowserActions> browser_actions_;
 
   std::unique_ptr<AccessibilityFocusHighlight> accessibility_focus_highlight_;
 
diff --git chrome/browser/ui/views/frame/browser_view_layout.cc chrome/browser/ui/views/frame/browser_view_layout.cc
index ab36dd2ae50e2..6dabacc9773fc 100644
--- chrome/browser/ui/views/frame/browser_view_layout.cc
+++ chrome/browser/ui/views/frame/browser_view_layout.cc
@@ -48,6 +48,10 @@
 #include "ui/views/window/client_view.h"
 #include "ui/views/window/hit_test_utils.h"
 
+#if BUILDFLAG(ENABLE_CEF)
+#include "cef/libcef/browser/chrome/views/chrome_views_util.h"
+#endif
+
 using views::View;
 using web_modal::ModalDialogHostObserver;
 using web_modal::WebContentsModalDialogHost;
@@ -578,6 +582,13 @@ int BrowserViewLayout::LayoutWebUITabStrip(int top) {
 
 int BrowserViewLayout::LayoutToolbar(int top) {
   TRACE_EVENT0("ui", "BrowserViewLayout::LayoutToolbar");
+#if BUILDFLAG(ENABLE_CEF)
+  if (cef::IsCefView(toolbar_)) {
+    // CEF may take ownership of the toolbar. Early exit to avoid the DCHECK
+    // in LayoutManager::SetViewVisibility().
+    return top;
+  }
+#endif
   int browser_view_width = vertical_layout_rect_.width();
   bool toolbar_visible = delegate_->IsToolbarVisible();
   int height = toolbar_visible ? toolbar_->GetPreferredSize().height() : 0;
diff --git chrome/browser/ui/views/frame/contents_web_view.cc chrome/browser/ui/views/frame/contents_web_view.cc
index 8267a265a8e10..ee08f18e96a34 100644
--- chrome/browser/ui/views/frame/contents_web_view.cc
+++ chrome/browser/ui/views/frame/contents_web_view.cc
@@ -23,6 +23,11 @@
 ContentsWebView::ContentsWebView(content::BrowserContext* browser_context)
     : views::WebView(browser_context),
       status_bubble_(nullptr) {
+  // Mouse events on draggable regions will not be handled by the WebView.
+  // Avoid the resulting DCHECK in NativeViewHost::OnMousePressed by
+  // configuring the NativeViewHost not to process events via the view
+  // hierarchy.
+  holder()->SetCanProcessEventsWithinSubtree(false);
 }
 
 ContentsWebView::~ContentsWebView() {
diff --git chrome/browser/ui/views/frame/picture_in_picture_browser_frame_view.cc chrome/browser/ui/views/frame/picture_in_picture_browser_frame_view.cc
index b9b50af047993..70ece4c81ff04 100644
--- chrome/browser/ui/views/frame/picture_in_picture_browser_frame_view.cc
+++ chrome/browser/ui/views/frame/picture_in_picture_browser_frame_view.cc
@@ -573,6 +573,11 @@ PictureInPictureBrowserFrameView::PictureInPictureBrowserFrameView(
   frame->GetNativeWindow()->SetEventTargeter(
       std::make_unique<chromeos::InteriorResizeHandleTargeter>());
 #endif
+
+  if (!browser_view->browser()->SupportsWindowFeature(
+          Browser::FEATURE_TITLEBAR)) {
+    top_bar_container_view_->SetVisible(false);
+  }
 }
 
 PictureInPictureBrowserFrameView::~PictureInPictureBrowserFrameView() {
@@ -669,18 +674,42 @@ gfx::Rect PictureInPictureBrowserFrameView::GetWindowBoundsForClientBounds(
 
 int PictureInPictureBrowserFrameView::NonClientHitTest(
     const gfx::Point& point) {
-  // Allow interacting with the buttons.
-  if (GetLocationIconViewBounds().Contains(point) ||
-      GetBackToTabControlsBounds().Contains(point) ||
-      GetCloseControlsBounds().Contains(point)) {
-    return HTCLIENT;
+  const bool frameless = !top_bar_container_view_->GetVisible();
+  if (!frameless) {
+    // Allow interacting with the buttons.
+    if (GetLocationIconViewBounds().Contains(point) ||
+        GetBackToTabControlsBounds().Contains(point) ||
+        GetCloseControlsBounds().Contains(point)) {
+      return HTCLIENT;
+    }
+
+    for (size_t i = 0; i < content_setting_views_.size(); i++) {
+      if (GetContentSettingViewBounds(i).Contains(point)) {
+        return HTCLIENT;
+      }
+    }
   }
 
-  for (size_t i = 0; i < content_setting_views_.size(); i++) {
-    if (GetContentSettingViewBounds(i).Contains(point)) {
-      return HTCLIENT;
+#if BUILDFLAG(ENABLE_CEF)
+  if (frameless) {
+    // Match logic in BrowserView::ShouldDescendIntoChildForEventHandling.
+    const auto draggable_region =
+        browser_view()->browser()->cef_delegate()->GetDraggableRegion();
+    if (draggable_region.has_value()) {
+      // Draggable regions are defined relative to the web contents.
+      gfx::Point point_in_contents_web_view_coords(point);
+      views::View::ConvertPointToTarget(GetWidget()->GetRootView(),
+                                        browser_view()->contents_web_view(),
+                                        &point_in_contents_web_view_coords);
+
+      if (draggable_region->contains(
+              point_in_contents_web_view_coords.x(),
+              point_in_contents_web_view_coords.y())) {
+        return HTCAPTION;
+      }
     }
   }
+#endif  // BUILDFLAG(ENABLE_CEF)
 
   // Allow dragging and resizing the window.
   int window_component = GetHTComponentForFrame(
@@ -747,7 +776,8 @@ void PictureInPictureBrowserFrameView::Layout() {
   gfx::Rect content_area = GetLocalBounds();
   content_area.Inset(FrameBorderInsets());
   gfx::Rect top_bar = content_area;
-  top_bar.set_height(kTopControlsHeight);
+  top_bar.set_height(
+      top_bar_container_view_->GetVisible() ? kTopControlsHeight : 0);
   top_bar_container_view_->SetBoundsRect(top_bar);
 #if !BUILDFLAG(IS_ANDROID)
   if (auto_pip_setting_overlay_) {
@@ -1207,7 +1237,8 @@ gfx::Insets PictureInPictureBrowserFrameView::ResizeBorderInsets() const {
 }
 
 int PictureInPictureBrowserFrameView::GetTopAreaHeight() const {
-  return FrameBorderInsets().top() + kTopControlsHeight;
+  return FrameBorderInsets().top() +
+         (top_bar_container_view_->GetVisible() ? kTopControlsHeight : 0);
 }
 
 gfx::Size PictureInPictureBrowserFrameView::GetNonClientViewAreaSize() const {
diff --git chrome/browser/ui/views/page_action/page_action_icon_controller.cc chrome/browser/ui/views/page_action/page_action_icon_controller.cc
index ca602db58de3a..1db448a2526a4 100644
--- chrome/browser/ui/views/page_action/page_action_icon_controller.cc
+++ chrome/browser/ui/views/page_action/page_action_icon_controller.cc
@@ -97,6 +97,12 @@ void PageActionIconController::Init(const PageActionIconParams& params,
   };
 
   for (PageActionIconType type : params.types_enabled) {
+#if BUILDFLAG(ENABLE_CEF)
+    if (params.browser && params.browser->cef_delegate() &&
+        !params.browser->cef_delegate()->IsPageActionIconVisible(type)) {
+      continue;
+    }
+#endif
     switch (type) {
       case PageActionIconType::kPaymentsOfferNotification:
         add_page_action_icon(
diff --git chrome/browser/ui/views/tabs/browser_tab_strip_controller.cc chrome/browser/ui/views/tabs/browser_tab_strip_controller.cc
index 734c741d1f2fa..739b468cfc0d8 100644
--- chrome/browser/ui/views/tabs/browser_tab_strip_controller.cc
+++ chrome/browser/ui/views/tabs/browser_tab_strip_controller.cc
@@ -560,29 +560,41 @@ gfx::Range BrowserTabStripController::ListTabsInGroup(
 }
 
 bool BrowserTabStripController::IsFrameCondensed() const {
+  if (!GetFrameView())
+    return false;
   return GetFrameView()->IsFrameCondensed();
 }
 
 bool BrowserTabStripController::HasVisibleBackgroundTabShapes() const {
+  if (!GetFrameView())
+    return false;
   return GetFrameView()->HasVisibleBackgroundTabShapes(
       BrowserFrameActiveState::kUseCurrent);
 }
 
 bool BrowserTabStripController::EverHasVisibleBackgroundTabShapes() const {
+  if (!GetFrameView())
+    return false;
   return GetFrameView()->EverHasVisibleBackgroundTabShapes();
 }
 
 bool BrowserTabStripController::CanDrawStrokes() const {
+  if (!GetFrameView())
+    return false;
   return GetFrameView()->CanDrawStrokes();
 }
 
 SkColor BrowserTabStripController::GetFrameColor(
     BrowserFrameActiveState active_state) const {
+  if (!GetFrameView())
+    return SK_ColorWHITE;
   return GetFrameView()->GetFrameColor(active_state);
 }
 
 absl::optional<int> BrowserTabStripController::GetCustomBackgroundId(
     BrowserFrameActiveState active_state) const {
+  if (!GetFrameView())
+    return absl::nullopt;
   return GetFrameView()->GetCustomBackgroundId(active_state);
 }
 
diff --git chrome/browser/ui/views/toolbar/toolbar_view.cc chrome/browser/ui/views/toolbar/toolbar_view.cc
index 26de912e300e9..c3761d1cb060c 100644
--- chrome/browser/ui/views/toolbar/toolbar_view.cc
+++ chrome/browser/ui/views/toolbar/toolbar_view.cc
@@ -186,7 +186,7 @@ class TabstripLikeBackground : public views::Background {
   void Paint(gfx::Canvas* canvas, views::View* view) const override {
     bool painted = TopContainerBackground::PaintThemeCustomImage(canvas, view,
                                                                  browser_view_);
-    if (!painted) {
+    if (!painted && browser_view_->frame()->GetFrameView()) {
       SkColor frame_color =
           browser_view_->frame()->GetFrameView()->GetFrameColor(
               BrowserFrameActiveState::kUseCurrent);
@@ -215,12 +215,13 @@ END_METADATA
 ////////////////////////////////////////////////////////////////////////////////
 // ToolbarView, public:
 
-ToolbarView::ToolbarView(Browser* browser, BrowserView* browser_view)
+ToolbarView::ToolbarView(Browser* browser, BrowserView* browser_view,
+                         absl::optional<DisplayMode> display_mode)
     : AnimationDelegateViews(this),
       browser_(browser),
       browser_view_(browser_view),
       app_menu_icon_controller_(browser->profile(), this),
-      display_mode_(GetDisplayMode(browser)) {
+      display_mode_(display_mode ? *display_mode : GetDisplayMode(browser)) {
   SetID(VIEW_ID_TOOLBAR);
 
   container_view_ = AddChildView(std::make_unique<ContainerView>());
@@ -245,6 +246,19 @@ ToolbarView::~ToolbarView() {
 }
 
 void ToolbarView::Init() {
+#if BUILDFLAG(ENABLE_CEF)
+  using ToolbarButtonType = cef::BrowserDelegate::ToolbarButtonType;
+  auto button_visible = [this](ToolbarButtonType type) {
+    if (this->browser_->cef_delegate()) {
+      return this->browser_->cef_delegate()->IsToolbarButtonVisible(type);
+    }
+    return true;
+  };
+  #define BUTTON_VISIBLE(type) button_visible(ToolbarButtonType::type)
+#else
+  #define BUTTON_VISIBLE(type) true
+#endif
+
 #if defined(USE_AURA)
   // Avoid generating too many occlusion tracking calculation events before this
   // function returns. The occlusion status will be computed only once once this
@@ -269,12 +283,13 @@ void ToolbarView::Init() {
 
   auto location_bar = std::make_unique<LocationBarView>(
       browser_, browser_->profile(), browser_->command_controller(), this,
-      display_mode_ != DisplayMode::NORMAL);
+      display_mode_ != DisplayMode::NORMAL && !browser_->toolbar_overridden());
   // Make sure the toolbar shows by default.
   size_animation_.Reset(1);
 
   std::unique_ptr<DownloadToolbarButtonView> download_button;
-  if (download::IsDownloadBubbleEnabled(browser_->profile())) {
+  if (download::IsDownloadBubbleEnabled(browser_->profile()) &&
+      BUTTON_VISIBLE(kDownload)) {
     download_button =
         std::make_unique<DownloadToolbarButtonView>(browser_view_);
   }
@@ -356,8 +371,10 @@ void ToolbarView::Init() {
     }
   }
   std::unique_ptr<media_router::CastToolbarButton> cast;
-  if (media_router::MediaRouterEnabled(browser_->profile()))
+  if (media_router::MediaRouterEnabled(browser_->profile()) &&
+      BUTTON_VISIBLE(kCast)) {
     cast = media_router::CastToolbarButton::Create(browser_);
+  }
 
   std::unique_ptr<MediaToolbarButtonView> media_button;
   if (base::FeatureList::IsEnabled(media::kGlobalMediaControls)) {
@@ -367,7 +384,8 @@ void ToolbarView::Init() {
 
   std::unique_ptr<send_tab_to_self::SendTabToSelfToolbarIconView>
       send_tab_to_self_button;
-  if (!browser_->profile()->IsOffTheRecord()) {
+  if (!browser_->profile()->IsOffTheRecord() &&
+      BUTTON_VISIBLE(kSendTabToSelf)) {
     send_tab_to_self_button =
         std::make_unique<send_tab_to_self::SendTabToSelfToolbarIconView>(
             browser_view_);
@@ -375,7 +393,7 @@ void ToolbarView::Init() {
 
   std::unique_ptr<SidePanelToolbarButton> side_panel_button;
   std::unique_ptr<SidePanelToolbarContainer> side_panel_toolbar_container;
-  if (browser_view_->unified_side_panel()) {
+  if (browser_view_->unified_side_panel() && BUTTON_VISIBLE(kSidePanel)) {
     if (base::FeatureList::IsEnabled(features::kSidePanelPinning)) {
       // TODO(b:299463334): Use the new SidePanelContainer which supports
       // ActionItems
diff --git chrome/browser/ui/views/toolbar/toolbar_view.h chrome/browser/ui/views/toolbar/toolbar_view.h
index 2bca1ba1b72eb..f7b0cf9d09e6e 100644
--- chrome/browser/ui/views/toolbar/toolbar_view.h
+++ chrome/browser/ui/views/toolbar/toolbar_view.h
@@ -91,7 +91,8 @@ class ToolbarView : public views::AccessiblePaneView,
                 // needs to be displayed.
   };
 
-  ToolbarView(Browser* browser, BrowserView* browser_view);
+  ToolbarView(Browser* browser, BrowserView* browser_view,
+              absl::optional<DisplayMode> display_mode);
   ToolbarView(const ToolbarView&) = delete;
   ToolbarView& operator=(const ToolbarView&) = delete;
   ~ToolbarView() override;
diff --git chrome/browser/ui/web_applications/draggable_region_host_impl.cc chrome/browser/ui/web_applications/draggable_region_host_impl.cc
index 460a2b08f964b..cb1b67d8b1213 100644
--- chrome/browser/ui/web_applications/draggable_region_host_impl.cc
+++ chrome/browser/ui/web_applications/draggable_region_host_impl.cc
@@ -11,6 +11,24 @@
 #include "chrome/common/chrome_features.h"
 #include "mojo/public/cpp/bindings/self_owned_receiver.h"
 
+namespace {
+
+bool IsSupported(Browser* browser) {
+  if (web_app::AppBrowserController::IsWebApp(browser))
+    return true;
+
+#if BUILDFLAG(ENABLE_CEF)
+  if (browser->cef_delegate() &&
+      browser->cef_delegate()->SupportsDraggableRegion()) {
+    return true;
+  }
+#endif
+
+  return false;
+}
+  
+}  // namespace
+
 DraggableRegionsHostImpl::DraggableRegionsHostImpl(
     content::RenderFrameHost& render_frame_host,
     mojo::PendingReceiver<chrome::mojom::DraggableRegions> receiver)
@@ -28,7 +46,7 @@ void DraggableRegionsHostImpl::CreateIfAllowed(
   auto* browser = chrome::FindBrowserWithWebContents(web_contents);
 
   // We only want to bind the receiver for PWAs.
-  if (!web_app::AppBrowserController::IsWebApp(browser))
+  if (!IsSupported(browser))
     return;
 
   // The object is bound to the lifetime of |render_frame_host| and the mojo
@@ -43,7 +61,7 @@ void DraggableRegionsHostImpl::UpdateDraggableRegions(
   auto* browser = chrome::FindBrowserWithWebContents(web_contents);
   // When a WebApp browser's WebContents is reparented to a tabbed browser, a
   // draggable regions update may race with the reparenting logic.
-  if (!web_app::AppBrowserController::IsWebApp(browser))
+  if (!IsSupported(browser))
     return;
 
   SkRegion sk_region;
@@ -56,5 +74,12 @@ void DraggableRegionsHostImpl::UpdateDraggableRegions(
   }
 
   auto* app_browser_controller = browser->app_controller();
-  app_browser_controller->UpdateDraggableRegion(sk_region);
+  if (app_browser_controller) {
+    app_browser_controller->UpdateDraggableRegion(sk_region);
+  }
+#if BUILDFLAG(ENABLE_CEF)
+  else {
+    browser->cef_delegate()->UpdateDraggableRegion(sk_region);
+  }
+#endif
 }