Don't use a sleep in the browser's main thread to throttle swapbuffers.

content/browser/renderer_host/render_widget_host_view_mac.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_VIEW_MAC_H_
 #define CONTENT_BROWSER_RENDERER_HOST_RENDER_WIDGET_HOST_VIEW_MAC_H_
 
 #import <Cocoa/Cocoa.h>
 #include <list>
 #include <map>
@@ skipping 320 matching lines @@
   // the next drawRect. Return true if the Ack should be sent, false if it
   // should be deferred until drawRect.
   bool CompositorSwapBuffers(uint64 surface_handle,
                              const gfx::Size& size,
                              float scale_factor,
                              const ui::LatencyInfo& latency_info);
   // Ack pending SwapBuffers requests, if any, to unblock the GPU process. Has
   // no effect if there are no pending requests.
   void AckPendingSwapBuffers();
 
+  // Ack pending SwapBuffers requests, but no more frequently than the vsync
+  // rate if the renderer is not throttling the swap rate.
+  void ThrottledAckPendingSwapBuffers();
+
   // Returns true and stores first rectangle for character range if the
   // requested |range| is already cached, otherwise returns false.
   // Exposed for testing.
   CONTENT_EXPORT bool GetCachedFirstRectForCharacterRange(
       NSRange range, NSRect* rect, NSRange* actual_range);
 
   // Returns true if there is line break in |range| and stores line breaking
   // point to |line_breaking_point|. The |line_break_point| is valid only if
   // this function returns true.
   bool GetLineBreakIndex(const std::vector<gfx::Rect>& bounds,
@@ skipping 78 matching lines @@
   float scale_factor() const;
 
   bool is_hidden() const { return is_hidden_; }
 
   void FrameSwapped();
 
  private:
   friend class RenderWidgetHostView;
   friend class RenderWidgetHostViewMacTest;
 
+  void GetVSyncParameters(
+      base::TimeTicks* timebase, base::TimeDelta* interval);
+
   // The view will associate itself with the given widget. The native view must
   // be hooked up immediately to the view hierarchy, or else when it is
   // deleted it will delete this out from under the caller.
   explicit RenderWidgetHostViewMac(RenderWidgetHost* widget);
 
   // Returns whether this render view is a popup (autocomplete window).
   bool IsPopup() const;
 
   // Shuts down the render_widget_host_.  This is a separate function so we can
   // invoke it from the message loop.
@@ skipping 51 matching lines @@
   // The fullscreen window used for pepper flash.
   scoped_nsobject<NSWindow> pepper_fullscreen_window_;
   scoped_nsobject<FullscreenWindowManager> fullscreen_window_manager_;
   // Our parent host view, if this is fullscreen.  NULL otherwise.
   RenderWidgetHostViewMac* fullscreen_parent_host_view_;
 
   // List of pending swaps for deferred acking:
   //   pairs of (route_id, gpu_host_id).
   std::list<std::pair<int32, int32> > pending_swap_buffers_acks_;
 
+  // Factory used to cancel outstanding throttled AckPendingSwapBuffers calls.
+  base::WeakPtrFactory<RenderWidgetHostViewMac>
+      pending_swap_buffers_acks_weak_factory_;
+
+  // The earliest time at which the next swap ack may be sent. Only relevant
+  // when swaps are not being throttled by the renderer (when threaded
+  // compositing is off).
+  base::Time next_swap_ack_time_;
+
   // The current composition character range and its bounds.
   ui::Range composition_range_;
   std::vector<gfx::Rect> composition_bounds_;
 
   // The current caret bounds.
   gfx::Rect caret_rect_;
 
   // Subscriber that listens to frame presentation events.
   scoped_ptr<RenderWidgetHostViewFrameSubscriber> frame_subscriber_;
 
   DISALLOW_COPY_AND_ASSIGN(RenderWidgetHostViewMac);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_RENDERER_HOST_RENDER_WIDGET_HOST_VIEW_MAC_H_