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..07d1287782867df5b50594a4d46c287d149a9bd6 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(bool physical_backing_resized);
+
   // 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

[aelias_OOO_until_Jul13, 2017/06/16 22:46:41]

I think there's a bug on the renderer side then.  CC is misreporting a frame as
being fullscreen in its metadata, when its size is still the old non-fullscreen
size.  Please find a way to defer the fullscreen metadata setting in the
renderer instead of working around the problem here.

[Khushal, 2017/06/19 18:46:34]

We use the state transitions in FullscreenController.h to set the fullscreen
state for a frame coming from the renderer. Are we doing something incorrect
there?

If the state reported in the CompositorFrame is correct then the scenario where
I expect waiting for a resize to help is the case where the renderer transitions
to fullscreen and sends a frame with the previous size before the android
Surface is resized.

[aelias_OOO_until_Jul13, 2017/06/19 19:01:32]

I'm not sure precisely what is going wrong, but it seems wrong in principle for
CC to report a frame with the non-fullscreen size as being fullscreen.  Instead
of waiting on the browser side for the size to change, I suggest something on
the renderer should be waiting for the size to change before flipping
is_fullscreen.

Or, what I would find even nicer is for is_fullscreen not be introduced at all,
for example if you use another signal like the transparency status of the
surface, or if you find a better way to obtain the expected final size on the
browser and then wait for all sizes to converge to it.

+  // 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;