Do not send a frame swap ack from the browser until the frame is drawn

content/browser/renderer_host/render_widget_host_impl.h

Index: content/browser/renderer_host/render_widget_host_impl.h
diff --git a/content/browser/renderer_host/render_widget_host_impl.h b/content/browser/renderer_host/render_widget_host_impl.h
index 546e2299737fdb679ed2c07c474d3c553076def6..3585a35b9c4fbafcc91a09376ab2f557db052d42 100644
--- a/content/browser/renderer_host/render_widget_host_impl.h
+++ b/content/browser/renderer_host/render_widget_host_impl.h
@@ -245,6 +245,11 @@ class CONTENT_EXPORT RenderWidgetHostImpl : virtual public RenderWidgetHost,
   // Indicates if the page has finished loading.
   void SetIsLoading(bool is_loading);
 
+  // Set a callback to be called before waiting for a backing store. This is
+  // only used by Mac to release renderer backpressure during resize.
+  void SetAboutToWaitForBackingStoreCallback(
+      const base::Closure& about_to_wait_for_backing_store_callback);

[piman, 2014/02/14 02:15:57]

Do you really need this? There's only a handful of callers of
GetBackingStore(true), you could SendPendingAcks before calling GetBackingStore
at these locations, no?

[ccameron, 2014/02/14 02:19:06]

See the remark in the .cc -- the caller we need is inside a loop inside RWHI

+
   // Check for the existance of a BackingStore of the given |desired_size| and
   // return it if it exists. If the BackingStore is GPU, true is returned and
   // |*backing_store| is set to NULL.
@@ -918,6 +923,8 @@ class CONTENT_EXPORT RenderWidgetHostImpl : virtual public RenderWidgetHost,
   // not sent to the renderer.
   bool has_touch_handler_;
 
+  base::Closure about_to_wait_for_backing_store_callback_;
+
   base::WeakPtrFactory<RenderWidgetHostImpl> weak_factory_;
 
   scoped_ptr<SyntheticGestureController> synthetic_gesture_controller_;