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

content/browser/renderer_host/render_widget_host_impl.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CONTENT_BROWSER_RENDERER_HOST_RENDER_WIDGET_HOST_IMPL_H_
 #define CONTENT_BROWSER_RENDERER_HOST_RENDER_WIDGET_HOST_IMPL_H_
 
 #include <deque>
 #include <list>
 #include <map>
@@ skipping 227 matching lines @@
   bool is_accelerated_compositing_active() {
     return is_accelerated_compositing_active_;
   }
 
   // Notifies the RenderWidgetHost that the View was destroyed.
   void ViewDestroyed();
 
   // 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.
   bool TryGetBackingStore(const gfx::Size& desired_size,
                           BackingStore** backing_store);
 
   // Get access to the widget's backing store matching the size of the widget's
   // view. If you pass |force_create| as true, then GetBackingStore may block
   // for the renderer to send a new frame. Otherwise, NULL will be returned if
   // the backing store doesn't already exist. It will also return NULL if the
@@ skipping 653 matching lines @@
   gfx::Vector2d last_scroll_offset_;
 
   bool pending_mouse_lock_request_;
   bool allow_privileged_mouse_lock_;
 
   // Keeps track of whether the webpage has any touch event handler. If it does,
   // then touch events are sent to the renderer. Otherwise, the touch events are
   // 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_;
 
   // Receives and handles all input events.
   scoped_ptr<InputRouter> input_router_;
 
   scoped_ptr<OverscrollController> overscroll_controller_;
 
   scoped_ptr<TimeoutMonitor> hang_monitor_timeout_;
 
 #if defined(OS_WIN)
   std::list<HWND> dummy_windows_for_activation_;
 #endif
 
   // List of callbacks for pending snapshot requests to the renderer.
   std::queue<base::Callback<void(bool, const SkBitmap&)> > pending_snapshots_;
 
   int64 last_input_number_;
 
   DISALLOW_COPY_AND_ASSIGN(RenderWidgetHostImpl);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_RENDERER_HOST_RENDER_WIDGET_HOST_IMPL_H_