Hide fullscreen rotation jank

content/browser/renderer_host/render_widget_host_view_android.h

Index: content/browser/renderer_host/render_widget_host_view_android.h
diff --git a/content/browser/renderer_host/render_widget_host_view_android.h b/content/browser/renderer_host/render_widget_host_view_android.h
index 6846edce443679b5027edc4a970db758f0052c54..9b2e0b85caadfa0bbe97b4c1345cc01e04a9a5f2 100644
--- a/content/browser/renderer_host/render_widget_host_view_android.h
+++ b/content/browser/renderer_host/render_widget_host_view_android.h
@@ -161,6 +161,7 @@ class CONTENT_EXPORT RenderWidgetHostViewAndroid
   std::unique_ptr<SyntheticGestureTarget> CreateSyntheticGestureTarget()
       override;
   void OnDidNavigateMainFrameToNewPage() override;
+  void OnFullscreenStateChanged(bool entered_fullscreen) override;
   void SetNeedsBeginFrames(bool needs_begin_frames) override;
   cc::FrameSinkId GetFrameSinkId() override;
   cc::FrameSinkId FrameSinkIdAtPoint(cc::SurfaceHittestDelegate* delegate,
@@ -238,6 +239,7 @@ class CONTENT_EXPORT RenderWidgetHostViewAndroid
   // Non-virtual methods
   void SetContentViewCore(ContentViewCoreImpl* content_view_core);
   SkColor GetCachedBackgroundColor() const;
+  bool CanShowThumbnailPlaceholder() const;
   void SendKeyEvent(const NativeWebKeyboardEvent& event);
   void SendMouseEvent(const ui::MotionEventAndroid&, int action_button);
   void SendMouseWheelEvent(const blink::WebMouseWheelEvent& event);
@@ -304,6 +306,14 @@ class CONTENT_EXPORT RenderWidgetHostViewAndroid
   cc::SurfaceId SurfaceIdForTesting() const override;
 
  private:
+  enum class FullscreenState {
+    kNotFullscreen,
+    kEnteringFullscreen,
+    kFullscreen,
+    kExitingFullscreen,
+    kFullscreenRotation,
+  };
+
   void RunAckCallbacks();
 
   void SendReclaimCompositorResources(bool is_swap_ack);
@@ -349,6 +359,8 @@ class CONTENT_EXPORT RenderWidgetHostViewAndroid
 
   WebContentsAccessibilityAndroid* GetWebContentsAccessibilityAndroid() const;
 
+  void UpdateFullscreenState();
+
   // The model object.
   RenderWidgetHostImpl* host_;
 
@@ -428,6 +440,21 @@ class CONTENT_EXPORT RenderWidgetHostViewAndroid
   float prev_top_shown_pix_;
   float prev_bottom_shown_pix_;
 
+  FullscreenState fullscreen_state_ = FullscreenState::kNotFullscreen;
+
+  // While we could simply take a mismatch in fullscreen states as the trigger
+  // for a transition, and assume the transition to have finished once the
+  // fullscreen states and sizes match, we have cases where we reach this
+  // consistent state before the physical backing size changes. Therefore we
+  // defer assuming the transition to be completed until a resize event is
+  // received, which is marked by |fullscreen_transition_awaiting_resize_|.
+  //
+  // Note that this assumes that every transition will be followed by a change
+  // in the view's physical backing size.
+  bool fullscreen_transition_awaiting_resize_ = false;
+  bool current_frame_is_fullscreen_ = false;
+  bool web_contents_is_fullscreen_ = false;
+
   cc::mojom::MojoCompositorFrameSinkClient* renderer_compositor_frame_sink_ =
       nullptr;