diff --git chrome/browser/ui/browser_command_controller.cc chrome/browser/ui/browser_command_controller.cc
index cfefe1f227283..402d848368269 100644
--- chrome/browser/ui/browser_command_controller.cc
+++ chrome/browser/ui/browser_command_controller.cc
@@ -351,8 +351,10 @@ bool BrowserCommandController::ExecuteCommandWithDisposition(
   // CommandUpdaterDelegate and CommandUpdater declare this function so we
   // choose to not implement CommandUpdaterDelegate inside this class and
   // therefore command_updater_ doesn't have the delegate set).
-  if (!SupportsCommand(id) || !IsCommandEnabled(id))
+  if (!SupportsCommand(id) || !IsCommandEnabled(id)) {
+    LOG(WARNING) << "Invalid/disabled command " << id;
     return false;
+  }
 
   // No commands are enabled if there is not yet any selected tab.
   // TODO(pkasting): It seems like we should not need this, because either
@@ -942,11 +944,13 @@ 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();
 }
 
 void BrowserCommandController::InitCommandState() {
diff --git chrome/browser/ui/views/frame/browser_frame.cc chrome/browser/ui/views/frame/browser_frame.cc
index 3fca382fde67e..6adddf506bb16 100644
--- chrome/browser/ui/views/frame/browser_frame.cc
+++ chrome/browser/ui/views/frame/browser_frame.cc
@@ -69,15 +69,23 @@ bool IsUsingGtkTheme(Profile* profile) {
 ////////////////////////////////////////////////////////////////////////////////
 // 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() {}
@@ -137,6 +145,12 @@ gfx::Rect BrowserFrame::GetBoundsForTabStripRegion(
 }
 
 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);
 }
 
@@ -171,15 +185,21 @@ void BrowserFrame::GetWindowPlacement(gfx::Rect* bounds,
 
 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();
 }
 
@@ -341,7 +361,8 @@ void BrowserFrame::SelectNativeTheme() {
   // Select between regular, dark and GTK theme.
   ui::NativeTheme* native_theme = ui::NativeTheme::GetInstanceForNativeUi();
 
-  if (browser_view_->browser()->profile()->IsIncognitoProfile()) {
+  if (browser_view_ &&
+      browser_view_->browser()->profile()->IsIncognitoProfile()) {
     // If the flag is enabled, then no matter if we are using the default theme
     // or not we always use the dark ui instance.
     if (base::FeatureList::IsEnabled(
diff --git chrome/browser/ui/views/frame/browser_frame.h chrome/browser/ui/views/frame/browser_frame.h
index 0ce7abdeb7d9f..8197a6bb7da98 100644
--- chrome/browser/ui/views/frame/browser_frame.h
+++ chrome/browser/ui/views/frame/browser_frame.h
@@ -54,7 +54,9 @@ 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() override;
 
   // Initialize the frame (creates the underlying native window).
diff --git chrome/browser/ui/views/frame/browser_view.cc chrome/browser/ui/views/frame/browser_view.cc
index e852eb7d20ed6..bb73d3055936d 100644
--- chrome/browser/ui/views/frame/browser_view.cc
+++ chrome/browser/ui/views/frame/browser_view.cc
@@ -586,11 +586,22 @@ 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)) {
+  if (browser)
+    InitBrowser(std::move(browser));
+}
+
+void BrowserView::InitBrowser(std::unique_ptr<Browser> browser) {
+  DCHECK(!browser_);
+  browser_ = std::move(browser);
+
+  immersive_mode_controller_ = chrome::CreateImmersiveModeController();
+
   SetShowIcon(::ShouldShowWindowIcon(browser_.get()));
 
   // In forced app mode, all size controls are always disabled. Otherwise, use
@@ -604,7 +615,6 @@ BrowserView::BrowserView(std::unique_ptr<Browser> browser)
   }
 
   browser_->tab_strip_model()->AddObserver(this);
-  immersive_mode_controller_ = chrome::CreateImmersiveModeController();
 
   // Top container holds tab strip region and toolbar and lives at the front of
   // the view hierarchy.
@@ -648,8 +658,15 @@ 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(browser_.get(), this);
+  if (!toolbar_) {
+    toolbar_ = new ToolbarView(browser_.get(), this, base::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_));
 
   contents_separator_ =
       top_container_->AddChildView(std::make_unique<ContentsSeparator>());
@@ -1430,6 +1447,8 @@ bool BrowserView::ShouldHideUIForFullscreen() const {
   if (immersive_mode_controller_->IsEnabled())
     return false;
 
+  if (!frame_->GetFrameView())
+    return false;
   return frame_->GetFrameView()->ShouldHideTopUIForFullscreen();
 }
 
@@ -2423,7 +2442,8 @@ BrowserView::GetNativeViewHostsForTopControlsSlide() const {
 }
 
 void BrowserView::ReparentTopContainerForEndOfImmersive() {
-  overlay_view_->SetVisible(false);
+  if (overlay_view_)
+    overlay_view_->SetVisible(false);
   top_container()->DestroyLayer();
   AddChildViewAt(top_container(), 0);
   EnsureFocusOrder();
@@ -2878,8 +2898,10 @@ 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();
 
   // Some of the situations when the BrowserView is laid out are:
   // - Enter/exit immersive fullscreen mode.
@@ -2942,6 +2964,11 @@ 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();
 
 #if BUILDFLAG(IS_CHROMEOS_ASH) || BUILDFLAG(IS_CHROMEOS_LACROS)
@@ -2977,13 +3004,9 @@ 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();
diff --git chrome/browser/ui/views/frame/browser_view.h chrome/browser/ui/views/frame/browser_view.h
index f6db8a6928831..a5302d7f73ba6 100644
--- chrome/browser/ui/views/frame/browser_view.h
+++ chrome/browser/ui/views/frame/browser_view.h
@@ -114,7 +114,9 @@ class BrowserView : public BrowserWindow,
                     public webapps::AppBannerManager::Observer {
  public:
   METADATA_HEADER(BrowserView);
+  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;
@@ -642,6 +644,12 @@ class BrowserView : public BrowserWindow,
     return accessibility_focus_highlight_.get();
   }
 
+ protected:
+  virtual ToolbarView* OverrideCreateToolbar(Browser* browser,
+                                             BrowserView* browser_view) {
+    return nullptr;
+  }
+
  private:
   // Do not friend BrowserViewLayout. Use the BrowserViewLayoutDelegate
   // interface to keep these two classes decoupled and testable.
diff --git chrome/browser/ui/views/frame/browser_view_layout.cc chrome/browser/ui/views/frame/browser_view_layout.cc
index 0e810789a99d7..14d69bd755fa2 100644
--- chrome/browser/ui/views/frame/browser_view_layout.cc
+++ chrome/browser/ui/views/frame/browser_view_layout.cc
@@ -420,6 +420,12 @@ int BrowserViewLayout::LayoutWebUITabStrip(int top) {
 
 int BrowserViewLayout::LayoutToolbar(int top) {
   TRACE_EVENT0("ui", "BrowserViewLayout::LayoutToolbar");
+  if (toolbar_->parent() && toolbar_->parent()->GetLayoutManager() != this &&
+      toolbar_->parent()->GetLayoutManager() != nullptr) {
+    // CEF may take ownership of the toolbar. Early exit to avoid the DCHECK
+    // in LayoutManager::SetViewVisibility().
+    return top;
+  }
   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/tabs/browser_tab_strip_controller.cc chrome/browser/ui/views/tabs/browser_tab_strip_controller.cc
index 50c10d73b9102..46f375b11d82c 100644
--- chrome/browser/ui/views/tabs/browser_tab_strip_controller.cc
+++ chrome/browser/ui/views/tabs/browser_tab_strip_controller.cc
@@ -582,37 +582,53 @@ 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::ShouldPaintAsActiveFrame() const {
+  if (!GetFrameView())
+    return false;
   return GetFrameView()->ShouldPaintAsActive();
 }
 
 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);
 }
 
 SkColor BrowserTabStripController::GetToolbarTopSeparatorColor() const {
+  if (!GetFrameView())
+    return SK_ColorWHITE;
   return GetFrameView()->GetToolbarTopSeparatorColor();
 }
 
 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 650fb98f63b0b..fd3d28bd70aac 100644
--- chrome/browser/ui/views/toolbar/toolbar_view.cc
+++ chrome/browser/ui/views/toolbar/toolbar_view.cc
@@ -160,12 +160,13 @@ auto& GetViewCommandMap() {
 ////////////////////////////////////////////////////////////////////////////////
 // ToolbarView, public:
 
-ToolbarView::ToolbarView(Browser* browser, BrowserView* browser_view)
+ToolbarView::ToolbarView(Browser* browser, BrowserView* browser_view,
+                         base::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);
 
   UpgradeDetector::GetInstance()->AddObserver(this);
@@ -198,7 +199,7 @@ void ToolbarView::Init() {
 #endif
   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);
 
diff --git chrome/browser/ui/views/toolbar/toolbar_view.h chrome/browser/ui/views/toolbar/toolbar_view.h
index c232c1c703500..d3b1593be5496 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,
+              base::Optional<DisplayMode> display_mode);
   ToolbarView(const ToolbarView&) = delete;
   ToolbarView& operator=(const ToolbarView&) = delete;
   ~ToolbarView() override;