diff --git chrome/browser/extensions/api/sessions/sessions_api.cc chrome/browser/extensions/api/sessions/sessions_api.cc
index 747d429ae99a5..c8dd80409068b 100644
--- chrome/browser/extensions/api/sessions/sessions_api.cc
+++ chrome/browser/extensions/api/sessions/sessions_api.cc
@@ -341,6 +341,7 @@ SessionsGetDevicesFunction::CreateWindowModel(
       state = api::windows::WindowState::kNormal;
       break;
     case ui::mojom::WindowShowState::kMinimized:
+    case ui::mojom::WindowShowState::kHidden:
       state = api::windows::WindowState::kMinimized;
       break;
     case ui::mojom::WindowShowState::kMaximized:
diff --git chrome/browser/ui/views/apps/chrome_native_app_window_views_aura.cc chrome/browser/ui/views/apps/chrome_native_app_window_views_aura.cc
index 6156dd1ccab4c..a2721ea15863e 100644
--- chrome/browser/ui/views/apps/chrome_native_app_window_views_aura.cc
+++ chrome/browser/ui/views/apps/chrome_native_app_window_views_aura.cc
@@ -43,6 +43,7 @@ ui::mojom::WindowShowState ChromeNativeAppWindowViewsAura::GetRestorableState(
 
     case ui::mojom::WindowShowState::kDefault:
     case ui::mojom::WindowShowState::kMinimized:
+    case ui::mojom::WindowShowState::kHidden:
     case ui::mojom::WindowShowState::kInactive:
     case ui::mojom::WindowShowState::kEnd:
       return ui::mojom::WindowShowState::kNormal;
diff --git components/sessions/core/session_service_commands.cc components/sessions/core/session_service_commands.cc
index 6b72cf19cf723..48f7f6f2c1f75 100644
--- components/sessions/core/session_service_commands.cc
+++ components/sessions/core/session_service_commands.cc
@@ -166,9 +166,10 @@ enum PersistedWindowShowState {
   PERSISTED_SHOW_STATE_MAXIMIZED = 3,
   // SHOW_STATE_INACTIVE (4) never persisted.
   PERSISTED_SHOW_STATE_FULLSCREEN = 5,
-  PERSISTED_SHOW_STATE_DETACHED_DEPRECATED = 6,
-  PERSISTED_SHOW_STATE_DOCKED_DEPRECATED = 7,
-  PERSISTED_SHOW_STATE_END = 8,
+  // SHOW_STATE_HIDDEN (6) never persisted.
+  PERSISTED_SHOW_STATE_DETACHED_DEPRECATED = 7,
+  PERSISTED_SHOW_STATE_DOCKED_DEPRECATED = 8,
+  PERSISTED_SHOW_STATE_END = 9,
 };
 
 // TODO(crbug.com/40946710): Remove this around December 2024. This is part of a
@@ -193,6 +194,7 @@ PersistedWindowShowState ShowStateToPersistedShowState(
     case ui::mojom::WindowShowState::kNormal:
       return PERSISTED_SHOW_STATE_NORMAL;
     case ui::mojom::WindowShowState::kMinimized:
+    case ui::mojom::WindowShowState::kHidden:
       return PERSISTED_SHOW_STATE_MINIMIZED;
     case ui::mojom::WindowShowState::kMaximized:
       return PERSISTED_SHOW_STATE_MAXIMIZED;
diff --git components/sessions/core/tab_restore_service_impl.cc components/sessions/core/tab_restore_service_impl.cc
index 514f81ee655f5..ba5ab6729b359 100644
--- components/sessions/core/tab_restore_service_impl.cc
+++ components/sessions/core/tab_restore_service_impl.cc
@@ -198,6 +198,7 @@ int SerializeWindowShowState(ui::mojom::WindowShowState show_state) {
     case ui::mojom::WindowShowState::kNormal:
       return kSerializedShowStateNormal;
     case ui::mojom::WindowShowState::kMinimized:
+    case ui::mojom::WindowShowState::kHidden:
       return kSerializedShowStateMinimized;
     case ui::mojom::WindowShowState::kMaximized:
       return kSerializedShowStateMaximized;
diff --git content/browser/renderer_host/render_widget_host_view_base.cc content/browser/renderer_host/render_widget_host_view_base.cc
index 72c5c119911a6..7c1bccc2a048e 100644
--- content/browser/renderer_host/render_widget_host_view_base.cc
+++ content/browser/renderer_host/render_widget_host_view_base.cc
@@ -590,6 +590,14 @@ float RenderWidgetHostViewBase::GetScaleOverrideForCapture() const {
   return scale_override_for_capture_;
 }
 
+void RenderWidgetHostViewBase::SetHasExternalParent(bool val) {
+  has_external_parent_ = val;
+}
+
+bool RenderWidgetHostViewBase::HasExternalParent() const {
+  return has_external_parent_;
+}
+
 void RenderWidgetHostViewBase::OnAutoscrollStart() {
   if (!GetMouseWheelPhaseHandler())
     return;
diff --git content/browser/renderer_host/render_widget_host_view_base.h content/browser/renderer_host/render_widget_host_view_base.h
index bdd8712db25a5..ae8a13e7f4c49 100644
--- content/browser/renderer_host/render_widget_host_view_base.h
+++ content/browser/renderer_host/render_widget_host_view_base.h
@@ -70,6 +70,7 @@ namespace content {
 class DevicePosturePlatformProvider;
 class MouseWheelPhaseHandler;
 class RenderWidgetHostImpl;
+class RenderWidgetHostViewGuest;
 class ScopedViewTransitionResources;
 class TextInputManager;
 class TouchSelectionControllerClientManager;
@@ -150,6 +151,9 @@ class CONTENT_EXPORT RenderWidgetHostViewBase
   float GetDeviceScaleFactor() const final;
   bool IsPointerLocked() override;
 
+  void SetHasExternalParent(bool val) override;
+  bool HasExternalParent() const override;
+
   // Identical to `CopyFromSurface()`, except that this method issues the
   // `viz::CopyOutputRequest` against the exact `viz::Surface` currently
   // embedded by this View, while `CopyFromSurface()` may return a copy of any
@@ -211,6 +215,10 @@ class CONTENT_EXPORT RenderWidgetHostViewBase
   // Called when screen information or native widget bounds change.
   virtual void UpdateScreenInfo();
 
+  // Generates the most current set of ScreenInfos from the current set of
+  // displays in the system for use in UpdateScreenInfo.
+  virtual display::ScreenInfos GetNewScreenInfosForUpdate();
+
   // Called by the TextInputManager to notify the view about being removed from
   // the list of registered views, i.e., TextInputManager is no longer tracking
   // TextInputState from this view. The RWHV should reset |text_input_manager_|
@@ -337,6 +345,12 @@ class CONTENT_EXPORT RenderWidgetHostViewBase
                            const gfx::Rect& bounds,
                            const gfx::Rect& anchor_rect) = 0;
 
+  // Perform all the initialization steps necessary for this object to represent
+  // the platform widget owned by |guest_view| and embedded in
+  // |parent_host_view|.
+  virtual void InitAsGuest(RenderWidgetHostView* parent_host_view,
+                           RenderWidgetHostViewGuest* guest_view) {}
+
   // Indicates whether the page has finished loading.
   virtual void SetIsLoading(bool is_loading) = 0;
 
@@ -587,6 +601,10 @@ class CONTENT_EXPORT RenderWidgetHostViewBase
   // to all displays.
   gfx::Size system_cursor_size_;
 
+  // True if the widget has a external parent view/window outside of the
+  // Chromium-controlled view/window hierarchy.
+  bool has_external_parent_ = false;
+
  private:
   FRIEND_TEST_ALL_PREFIXES(
       BrowserSideFlingBrowserTest,
@@ -608,10 +626,6 @@ class CONTENT_EXPORT RenderWidgetHostViewBase
 
   void SynchronizeVisualProperties();
 
-  // Generates the most current set of ScreenInfos from the current set of
-  // displays in the system for use in UpdateScreenInfo.
-  display::ScreenInfos GetNewScreenInfosForUpdate();
-
   // Called when display properties that need to be synchronized with the
   // renderer process changes. This method is called before notifying
   // RenderWidgetHostImpl in order to allow the view to allocate a new
diff --git content/browser/renderer_host/render_widget_host_view_event_handler.cc content/browser/renderer_host/render_widget_host_view_event_handler.cc
index a131d58351110..196fe4d25d4a7 100644
--- content/browser/renderer_host/render_widget_host_view_event_handler.cc
+++ content/browser/renderer_host/render_widget_host_view_event_handler.cc
@@ -52,6 +52,10 @@ namespace {
 // of the border area, in percentage of the corresponding dimension.
 const int kMouseLockBorderPercentage = 15;
 
+#if BUILDFLAG(IS_LINUX)
+#include "ui/aura/window_tree_host.h"
+#endif
+
 #if BUILDFLAG(IS_WIN)
 // A callback function for EnumThreadWindows to enumerate and dismiss
 // any owned popup windows.
@@ -827,6 +831,14 @@ void RenderWidgetHostViewEventHandler::MoveCursorToCenter(
     }
     return;
   }
+#endif
+#if BUILDFLAG(IS_LINUX)
+  if (host_view_->HasExternalParent() &&
+      window_ && window_->delegate()->CanFocus()) {
+    aura::WindowTreeHost* host = window_->GetHost();
+    if (host)
+      host->Show();
+  }
 #endif
   synthetic_move_position_ = center_in_screen;
 }
@@ -857,6 +869,17 @@ bool RenderWidgetHostViewEventHandler::MatchesSynthesizedMovePosition(
 }
 
 void RenderWidgetHostViewEventHandler::SetKeyboardFocus() {
+#if BUILDFLAG(IS_WIN)
+  if (host_view_->HasExternalParent() &&
+      window_ && window_->delegate()->CanFocus()) {
+    aura::WindowTreeHost* host = window_->GetHost();
+    if (host) {
+      gfx::AcceleratedWidget hwnd = host->GetAcceleratedWidget();
+      if (!(::GetWindowLong(hwnd, GWL_EXSTYLE) & WS_EX_NOACTIVATE))
+        ::SetFocus(hwnd);
+    }
+  }
+#endif
   // TODO(wjmaclean): can host_ ever be null?
   if (host_ && set_focus_on_mouse_down_or_key_event_) {
     set_focus_on_mouse_down_or_key_event_ = false;
diff --git content/public/browser/render_widget_host_view.h content/public/browser/render_widget_host_view.h
index b4ff7c11d8e3c..b21417f89e6e1 100644
--- content/public/browser/render_widget_host_view.h
+++ content/public/browser/render_widget_host_view.h
@@ -254,6 +254,14 @@ class CONTENT_EXPORT RenderWidgetHostView {
   // This must always return the same device scale factor as GetScreenInfo.
   virtual float GetDeviceScaleFactor() const = 0;
 
+  // Set whether the widget has a external parent view/window outside of the
+  // Chromium-controlled view/window hierarchy.
+  virtual void SetHasExternalParent(bool val) = 0;
+
+  // Returns true if the widget has a external parent view/window outside of the
+  // Chromium-controlled view/window hierarchy.
+  virtual bool HasExternalParent() const = 0;
+
 #if BUILDFLAG(IS_MAC)
   // Set the view's active state (i.e., tint state of controls).
   virtual void SetActive(bool active) = 0;
diff --git ui/aura/native_window_occlusion_tracker_win.cc ui/aura/native_window_occlusion_tracker_win.cc
index e9bb4ee5bccee..e6172b1a8d53f 100644
--- ui/aura/native_window_occlusion_tracker_win.cc
+++ ui/aura/native_window_occlusion_tracker_win.cc
@@ -102,6 +102,13 @@ void NativeWindowOcclusionTrackerWin::Enable(Window* window) {
   // when it's no longer true that all windows are minimized, and when the
   // window is destroyed.
   HWND root_window_hwnd = window->GetHost()->GetAcceleratedWidget();
+
+  // Delay occlusion tracking for initially-minimized windows.
+  // See CEF issue #3638.
+  if (IsIconic(root_window_hwnd)) {
+    return;
+  }
+
   window->AddObserver(this);
   // Remember this mapping from hwnd to Window*.
   hwnd_root_window_map_[root_window_hwnd] = window;
diff --git ui/base/mojom/window_show_state.mojom ui/base/mojom/window_show_state.mojom
index 526b6129d6d01..1937a441b930d 100644
--- ui/base/mojom/window_show_state.mojom
+++ ui/base/mojom/window_show_state.mojom
@@ -23,6 +23,7 @@ enum WindowShowState {
   kMaximized = 3,
   kInactive = 4, // Views only, not persisted.
   kFullscreen = 5,
+  kHidden = 6,
   // TODO(crbug.com/361560784): Investigate and Remove `kEnd`
-  [MinVersion=1] kEnd = 6,
+  [MinVersion=1] kEnd = 7,
 };
diff --git ui/ozone/platform/x11/x11_window.cc ui/ozone/platform/x11/x11_window.cc
index c21f3aa2e68f7..0a2443e772767 100644
--- ui/ozone/platform/x11/x11_window.cc
+++ ui/ozone/platform/x11/x11_window.cc
@@ -1860,7 +1860,8 @@ void X11Window::CreateXWindow(const PlatformWindowInitProperties& properties) {
   req.border_pixel = 0;
 
   bounds_in_pixels_ = SanitizeBounds(bounds);
-  req.parent = x_root_window_;
+  req.parent = properties.parent_widget == gfx::kNullAcceleratedWidget ?
+      x_root_window_ : static_cast<x11::Window>(properties.parent_widget);
   req.x = bounds_in_pixels_.x();
   req.y = bounds_in_pixels_.y();
   req.width = bounds_in_pixels_.width();
diff --git ui/views/widget/desktop_aura/desktop_screen_win.cc ui/views/widget/desktop_aura/desktop_screen_win.cc
index e31c5b4cb6726..1b724948c2868 100644
--- ui/views/widget/desktop_aura/desktop_screen_win.cc
+++ ui/views/widget/desktop_aura/desktop_screen_win.cc
@@ -23,6 +23,8 @@ DesktopScreenWin::~DesktopScreenWin() {
 }
 
 HWND DesktopScreenWin::GetHWNDFromNativeWindow(gfx::NativeWindow window) const {
+  if (!window)
+    return nullptr;
   aura::WindowTreeHost* host = window->GetHost();
   return host ? host->GetAcceleratedWidget() : nullptr;
 }
diff --git ui/views/widget/desktop_aura/desktop_window_tree_host_linux.cc ui/views/widget/desktop_aura/desktop_window_tree_host_linux.cc
index feffe48a5695d..69a544dba8fb1 100644
--- ui/views/widget/desktop_aura/desktop_window_tree_host_linux.cc
+++ ui/views/widget/desktop_aura/desktop_window_tree_host_linux.cc
@@ -193,6 +193,18 @@ Widget::MoveLoopResult DesktopWindowTreeHostLinux::RunMoveLoop(
   return result;
 }
 
+gfx::Rect DesktopWindowTreeHostLinux::GetWindowBoundsInScreen() const {
+  if (!screen_bounds_.IsEmpty())
+    return screen_bounds_;
+  return DesktopWindowTreeHostPlatform::GetWindowBoundsInScreen();
+}
+
+gfx::Point DesktopWindowTreeHostLinux::GetLocationOnScreenInPixels() const {
+  if (!screen_bounds_.IsEmpty())
+    return screen_bounds_.origin();
+  return DesktopWindowTreeHostPlatform::GetLocationOnScreenInPixels();
+}
+
 void DesktopWindowTreeHostLinux::DispatchEvent(ui::Event* event) {
   // In Windows, the native events sent to chrome are separated into client
   // and non-client versions of events, which we record on our LocatedEvent
@@ -328,6 +340,8 @@ void DesktopWindowTreeHostLinux::AddAdditionalInitProperties(
 
   properties->wayland_app_id = params.wayland_app_id;
 
+  properties->parent_widget = params.parent_widget;
+
   DCHECK(!properties->x11_extension_delegate);
   properties->x11_extension_delegate = this;
 }
diff --git ui/views/widget/desktop_aura/desktop_window_tree_host_linux.h ui/views/widget/desktop_aura/desktop_window_tree_host_linux.h
index 590f97eee1fda..3980e814e80b9 100644
--- ui/views/widget/desktop_aura/desktop_window_tree_host_linux.h
+++ ui/views/widget/desktop_aura/desktop_window_tree_host_linux.h
@@ -63,6 +63,8 @@ class VIEWS_EXPORT DesktopWindowTreeHostLinux
   // client-drawn shadow.
   virtual void UpdateFrameHints();
 
+  void set_screen_bounds(const gfx::Rect& bounds) { screen_bounds_ = bounds; }
+
  protected:
   // Overridden from DesktopWindowTreeHost:
   void Init(const Widget::InitParams& params) override;
@@ -72,6 +74,8 @@ class VIEWS_EXPORT DesktopWindowTreeHostLinux
       const gfx::Vector2d& drag_offset,
       Widget::MoveLoopSource source,
       Widget::MoveLoopEscapeBehavior escape_behavior) override;
+  gfx::Rect GetWindowBoundsInScreen() const override;
+  gfx::Point GetLocationOnScreenInPixels() const override;
 
   // PlatformWindowDelegate:
   void DispatchEvent(ui::Event* event) override;
@@ -121,6 +125,9 @@ class VIEWS_EXPORT DesktopWindowTreeHostLinux
 
   uint32_t modal_dialog_counter_ = 0;
 
+   // Override the screen bounds when the host is a child window.
+  gfx::Rect screen_bounds_;
+
   // The display and the native X window hosting the root window.
   base::WeakPtrFactory<DesktopWindowTreeHostLinux> weak_factory_{this};
 };
diff --git ui/views/widget/desktop_aura/desktop_window_tree_host_platform.cc ui/views/widget/desktop_aura/desktop_window_tree_host_platform.cc
index 628494b15591f..32cbfb8314439 100644
--- ui/views/widget/desktop_aura/desktop_window_tree_host_platform.cc
+++ ui/views/widget/desktop_aura/desktop_window_tree_host_platform.cc
@@ -282,8 +282,8 @@ void DesktopWindowTreeHostPlatform::Init(const Widget::InitParams& params) {
   if (properties.parent_widget) {
     window_parent_ = DesktopWindowTreeHostPlatform::GetHostForWidget(
         properties.parent_widget);
-    DCHECK(window_parent_);
-    window_parent_->window_children_.insert(this);
+    if (window_parent_)
+      window_parent_->window_children_.insert(this);
   }
 
   // Calculate initial bounds.
diff --git ui/views/widget/desktop_aura/desktop_window_tree_host_win.cc ui/views/widget/desktop_aura/desktop_window_tree_host_win.cc
index 6cd2eace306cb..a6246e6cb6f3f 100644
--- ui/views/widget/desktop_aura/desktop_window_tree_host_win.cc
+++ ui/views/widget/desktop_aura/desktop_window_tree_host_win.cc
@@ -20,6 +20,7 @@
 #include "ui/aura/client/aura_constants.h"
 #include "ui/aura/client/cursor_client.h"
 #include "ui/aura/client/focus_client.h"
+#include "ui/aura/native_window_occlusion_tracker.h"
 #include "ui/aura/window_event_dispatcher.h"
 #include "ui/base/class_property.h"
 #include "ui/base/cursor/cursor.h"
@@ -185,22 +186,42 @@ void DesktopWindowTreeHostWin::Init(const Widget::InitParams& params) {
                         native_widget_delegate_.get());
 
   HWND parent_hwnd = nullptr;
-  if (params.parent && params.parent->GetHost())
+  if (params.parent_widget) {
+    parent_hwnd = params.parent_widget;
+    has_external_parent_ = true;
+  } else if (params.parent && params.parent->GetHost()) {
     parent_hwnd = params.parent->GetHost()->GetAcceleratedWidget();
+  }
 
   remove_standard_frame_ = params.remove_standard_frame;
   has_non_client_view_ = Widget::RequiresNonClientView(params.type);
   z_order_ = params.EffectiveZOrderLevel();
 
-  // We don't have an HWND yet, so scale relative to the nearest screen.
-  gfx::Rect pixel_bounds =
-      display::win::ScreenWin::DIPToScreenRect(nullptr, params.bounds);
+  gfx::Rect pixel_bounds;
+  if (has_external_parent_ && params.type != Widget::InitParams::TYPE_MENU) {
+    // Scale relative to the screen that contains the parent window.
+    // Child windows always have origin (0,0).
+    pixel_bounds.set_size(display::win::ScreenWin::DIPToScreenSize(
+        parent_hwnd, params.bounds.size()));
+  } else {
+    // We don't have an HWND yet, so scale relative to the nearest screen.
+    pixel_bounds =
+        display::win::ScreenWin::DIPToScreenRect(nullptr, params.bounds);
+  }
+
   message_handler_->Init(parent_hwnd, pixel_bounds);
   CreateCompositor(params.force_software_compositing);
   OnAcceleratedWidgetAvailable();
   InitHost();
   window()->Show();
 
+  if (params.show_state == ui::mojom::WindowShowState::kMinimized) {
+    // Delay enablement of native occlusion tracking until the
+    // initially-minimized window is restored for the first time.
+    // See CEF issue #3638.
+    initially_minimized_first_restore_pending_ = true;
+  }
+
   // Stack immediately above its parent so that it does not cover other
   // root-level windows, with the exception of menus, to allow them to be
   // displayed on top of other windows.
@@ -1078,10 +1099,23 @@ void DesktopWindowTreeHostWin::HandleWindowMinimizedOrRestored(bool restored) {
   if (!native_widget_delegate_->IsNativeWidgetInitialized())
     return;
 
-  if (restored)
+  if (restored) {
     window()->Show();
-  else
+
+    if (initially_minimized_first_restore_pending_) {
+      initially_minimized_first_restore_pending_ = false;
+
+      // Enable native occlusion tracking for initially-minimized windows here
+      // to avoid incorrect hidden state after restore. See CEF issue #3638.
+      if (aura::NativeWindowOcclusionTracker::
+              IsNativeWindowOcclusionTrackingAlwaysEnabled(this)) {
+        aura::NativeWindowOcclusionTracker::
+            EnableNativeWindowOcclusionTracking(this);
+      }
+    }
+  } else {
     window()->Hide();
+  }
 }
 
 void DesktopWindowTreeHostWin::HandleClientSizeChanged(
@@ -1099,11 +1133,15 @@ void DesktopWindowTreeHostWin::HandleFrameChanged() {
 }
 
 void DesktopWindowTreeHostWin::HandleNativeFocus(HWND last_focused_window) {
-  // TODO(beng): inform the native_widget_delegate_.
+  // See comments in CefBrowserPlatformDelegateNativeWin::SetFocus.
+  if (has_external_parent_ && CanActivate())
+    HandleActivationChanged(true);
 }
 
 void DesktopWindowTreeHostWin::HandleNativeBlur(HWND focused_window) {
-  // TODO(beng): inform the native_widget_delegate_.
+  // See comments in CefBrowserPlatformDelegateNativeWin::SetFocus.
+  if (has_external_parent_ && CanActivate())
+    HandleActivationChanged(false);
 }
 
 bool DesktopWindowTreeHostWin::HandleMouseEvent(ui::MouseEvent* event) {
@@ -1111,6 +1149,12 @@ bool DesktopWindowTreeHostWin::HandleMouseEvent(ui::MouseEvent* event) {
   if (ui::PlatformEventSource::ShouldIgnoreNativePlatformEvents())
     return true;
 
+  // See comments in CefBrowserPlatformDelegateNativeWin::SetFocus.
+  if (has_external_parent_ && CanActivate() && event->IsAnyButton() &&
+      ::GetFocus() != GetHWND()) {
+    ::SetFocus(GetHWND());
+  }
+
   SendEventToSink(event);
   return event->handled();
 }
@@ -1293,9 +1337,17 @@ void DesktopWindowTreeHostWin::SetBoundsInDIP(const gfx::Rect& bounds) {
   // positions in variable-DPI situations. See https://crbug.com/1224715 for
   // details.
   aura::Window* root = nullptr;
-  const gfx::Rect bounds_in_pixels =
+  if (has_external_parent_) {
+    // Scale relative to the screen that contains the parent window.
+    root = AsWindowTreeHost()->window();
+  }
+  gfx::Rect bounds_in_pixels =
       display::Screen::GetScreen()->DIPToScreenRectInWindow(
           root, AdjustedContentBounds(bounds));
+  if (has_external_parent_) {
+    // Child windows always have origin (0,0).
+    bounds_in_pixels.set_origin(gfx::Point(0, 0));
+  }
   AsWindowTreeHost()->SetBoundsInPixels(bounds_in_pixels);
 }
 
diff --git ui/views/widget/desktop_aura/desktop_window_tree_host_win.h ui/views/widget/desktop_aura/desktop_window_tree_host_win.h
index 1e2c5bb35cc31..e73afc2d303ac 100644
--- ui/views/widget/desktop_aura/desktop_window_tree_host_win.h
+++ ui/views/widget/desktop_aura/desktop_window_tree_host_win.h
@@ -336,6 +336,14 @@ class VIEWS_EXPORT DesktopWindowTreeHostWin
   // True if the window is allow to take screenshots, by default is true.
   bool allow_screenshots_ = true;
 
+  // True if the widget has a external parent view/window outside of the
+  // Chromium-controlled view/window hierarchy.
+  bool has_external_parent_ = false;
+
+  // True if the first call to HandleWindowMinimizedOrRestored for an initially-
+  // minimized window is pending.
+  bool initially_minimized_first_restore_pending_ = false;
+
   // Visibility of the cursor. On Windows we can have multiple root windows and
   // the implementation of ::ShowCursor() is based on a counter, so making this
   // member static ensures that ::ShowCursor() is always called exactly once
diff --git ui/views/widget/native_widget_mac.mm ui/views/widget/native_widget_mac.mm
index 85c36216bbadf..2f6b48b656102 100644
--- ui/views/widget/native_widget_mac.mm
+++ ui/views/widget/native_widget_mac.mm
@@ -662,6 +662,7 @@ void NativeWidgetMac::Show(ui::mojom::WindowShowState show_state,
       break;
     case ui::mojom::WindowShowState::kMaximized:
     case ui::mojom::WindowShowState::kFullscreen:
+    case ui::mojom::WindowShowState::kHidden:
       NOTIMPLEMENTED();
       break;
     case ui::mojom::WindowShowState::kEnd:
diff --git ui/views/widget/widget.cc ui/views/widget/widget.cc
index ed69823cc34d7..116588f1f9e45 100644
--- ui/views/widget/widget.cc
+++ ui/views/widget/widget.cc
@@ -423,7 +423,8 @@ void Widget::Init(InitParams params) {
   }
 
   params.child |= (params.type == InitParams::TYPE_CONTROL);
-  is_top_level_ = !params.child;
+  is_top_level_ = !params.child ||
+                  params.parent_widget != gfx::kNullAcceleratedWidget;
   is_headless_ = params.ShouldInitAsHeadless();
   is_autosized_ = params.autosize;
 
@@ -530,9 +531,14 @@ void Widget::Init(InitParams params) {
 
     if (show_state == ui::mojom::WindowShowState::kMaximized) {
       Maximize();
+      saved_show_state_ = ui::mojom::WindowShowState::kMaximized;
     } else if (show_state == ui::mojom::WindowShowState::kMinimized) {
       Minimize();
       saved_show_state_ = ui::mojom::WindowShowState::kMinimized;
+    } else if (show_state == ui::mojom::WindowShowState::kFullscreen) {
+      SetFullscreen(true);
+    } else if (show_state == ui::mojom::WindowShowState::kHidden) {
+      Hide();
     }
 
 #if BUILDFLAG(IS_CHROMEOS_ASH)
@@ -546,7 +552,12 @@ void Widget::Init(InitParams params) {
   } else if (delegate) {
     SetContentsView(delegate->TransferOwnershipOfContentsView());
     if (should_set_initial_bounds) {
-      SetInitialBoundsForFramelessWindow(bounds);
+      if (params.parent_widget != gfx::kNullAcceleratedWidget) {
+        // Set the bounds directly instead of applying an inset.
+        SetBounds(bounds);
+      } else {
+        SetInitialBoundsForFramelessWindow(bounds);
+      }
     }
   }
 
@@ -1736,10 +1747,16 @@ void Widget::OnNativeWidgetParentChanged(gfx::NativeView parent) {
 }
 
 gfx::Size Widget::GetMinimumSize() const {
+  gfx::Size size;
+  if (widget_delegate_->MaybeGetMinimumSize(&size))
+    return size;
   return non_client_view_ ? non_client_view_->GetMinimumSize() : gfx::Size();
 }
 
 gfx::Size Widget::GetMaximumSize() const {
+  gfx::Size size;
+  if (widget_delegate_->MaybeGetMaximumSize(&size))
+    return size;
   return non_client_view_ ? non_client_view_->GetMaximumSize() : gfx::Size();
 }
 
@@ -1990,7 +2007,8 @@ bool Widget::SetInitialFocus(ui::mojom::WindowShowState show_state) {
   View* v = widget_delegate_->GetInitiallyFocusedView();
   if (!focus_on_creation_ ||
       show_state == ui::mojom::WindowShowState::kInactive ||
-      show_state == ui::mojom::WindowShowState::kMinimized) {
+      show_state == ui::mojom::WindowShowState::kMinimized  ||
+      show_state == ui::mojom::WindowShowState::kHidden) {
     // If not focusing the window now, tell the focus manager which view to
     // focus when the window is restored.
     if (v)
diff --git ui/views/widget/widget.h ui/views/widget/widget.h
index 42c7ccb7a26f0..0483a550d415f 100644
--- ui/views/widget/widget.h
+++ ui/views/widget/widget.h
@@ -366,6 +366,8 @@ class VIEWS_EXPORT Widget : public internal::NativeWidgetDelegate,
     // the concept with bubble anchoring a la BubbleDialogDelegateView.
     gfx::NativeView parent = gfx::NativeView();
 
+    gfx::AcceleratedWidget parent_widget = gfx::kNullAcceleratedWidget;
+
     // Specifies the initial bounds of the Widget. Default is empty, which means
     // the NativeWidget may specify a default size. If the parent is specified,
     // |bounds| is in the parent's coordinate system. If the parent is not
@@ -779,7 +781,7 @@ class VIEWS_EXPORT Widget : public internal::NativeWidgetDelegate,
   void ShowInactive();
 
   // Activates the widget, assuming it already exists and is visible.
-  void Activate();
+  virtual void Activate();
 
   // Deactivates the widget, making the next window in the Z order the active
   // window.
diff --git ui/views/widget/widget_delegate.h ui/views/widget/widget_delegate.h
index 336b820e995f1..d08c1e7e7cd6e 100644
--- ui/views/widget/widget_delegate.h
+++ ui/views/widget/widget_delegate.h
@@ -396,6 +396,10 @@ class VIEWS_EXPORT WidgetDelegate {
   // Returns true if the title text should be centered.
   bool ShouldCenterWindowTitleText() const;
 
+  // CEF supports override of min/max size values.
+  virtual bool MaybeGetMinimumSize(gfx::Size* size) const { return false; }
+  virtual bool MaybeGetMaximumSize(gfx::Size* size) const { return false; }
+
   bool focus_traverses_out() const { return params_.focus_traverses_out; }
   bool enable_arrow_key_traversal() const {
     return params_.enable_arrow_key_traversal;
diff --git ui/views/widget/widget_hwnd_utils.cc ui/views/widget/widget_hwnd_utils.cc
index f28c1d1fb5581..4e2390b94cbe9 100644
--- ui/views/widget/widget_hwnd_utils.cc
+++ ui/views/widget/widget_hwnd_utils.cc
@@ -64,7 +64,8 @@ void CalculateWindowStylesFromInitParams(
       if (!widget_delegate->CanResize())
         *style &= static_cast<DWORD>(~(WS_THICKFRAME | WS_MAXIMIZEBOX));
       if (params.remove_standard_frame)
-        *style &= static_cast<DWORD>(~(WS_MINIMIZEBOX | WS_MAXIMIZEBOX));
+        *style &= static_cast<DWORD>(~(WS_MINIMIZEBOX | WS_MAXIMIZEBOX |
+                                       WS_CAPTION | WS_SYSMENU));
 
       if (native_widget_delegate->IsDialogBox()) {
         *style |= DS_MODALFRAME;
diff --git ui/views/win/hwnd_message_handler.cc ui/views/win/hwnd_message_handler.cc
index 328cf96499fa2..879fb9820ee38 100644
--- ui/views/win/hwnd_message_handler.cc
+++ ui/views/win/hwnd_message_handler.cc
@@ -774,7 +774,11 @@ bool HWNDMessageHandler::IsVisible() const {
 }
 
 bool HWNDMessageHandler::IsActive() const {
-  return ::GetActiveWindow() == hwnd();
+  // This active state is checked via FocusManager::SetFocusedViewWithReason.
+  // With CEF external parent hwnd() may be a child window, whereas
+  // GetActiveWindow() will return the root window, so make sure that we always
+  // compare root windows.
+  return ::GetActiveWindow() == ::GetAncestor(hwnd(), GA_ROOT);
 }
 
 bool HWNDMessageHandler::IsMinimized() const {
@@ -3229,10 +3233,13 @@ LRESULT HWNDMessageHandler::HandleMouseEventInternal(UINT message,
   } else if (event.type() == ui::EventType::kMousewheel) {
     ui::MouseWheelEvent mouse_wheel_event(msg);
     // Reroute the mouse wheel to the window under the pointer if applicable.
-    return (ui::RerouteMouseWheel(hwnd(), w_param, l_param) ||
-            delegate_->HandleMouseEvent(&mouse_wheel_event))
-               ? 0
-               : 1;
+    if (ui::RerouteMouseWheel(hwnd(), w_param, l_param) ||
+        delegate_->HandleMouseEvent(&mouse_wheel_event)) {
+      SetMsgHandled(TRUE);
+      return 0;
+    } else {
+      return 1;
+    }
   }
 
   // Suppress |EventType::kMouseMoved| and |EventType::kMouseDragged| events