Avoid Copying damage rect when using Overlays

content/common/gpu/image_transport_surface_overlay_mac.mm

 // Copyright 2015 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.
 
 #include "content/common/gpu/image_transport_surface_overlay_mac.h"
 
 #include <algorithm>
 #include <IOSurface/IOSurface.h>
 #include <OpenGL/CGLRenderers.h>
 #include <OpenGL/CGLTypes.h>
@@ skipping 340 matching lines @@
   }
 
   // Update the plane lists.
   {
     // Sort the input planes by z-index, and remove any overlays from the
     // damage rect.
     gfx::RectF dip_damage_rect = ConvertRectToDIPF(
         swap->scale_factor, swap->pixel_damage_rect);
     std::sort(swap->overlay_planes.begin(), swap->overlay_planes.end(),
               OverlayPlane::Compare);
-    for (auto& plane : swap->overlay_planes)
-      dip_damage_rect.Subtract(plane->dip_frame_rect);
 
     ScopedCAActionDisabler disabler;
     if (swap->root_plane.get())
       UpdateRootAndPartialDamagePlanes(swap->root_plane, dip_damage_rect);
     UpdateOverlayPlanes(swap->overlay_planes);
     UpdateCALayerTree();
     swap->overlay_planes.clear();
   }
 
   // Send acknowledgement to the browser.
@@ skipping 334 matching lines @@
   // Compute the previous vsync time.
   base::TimeTicks previous_vsync =
       vsync_interval_ * ((from - vsync_timebase_) / vsync_interval_) +
       vsync_timebase_;
 
   // Return |interval_fraction| through the next vsync.
   return previous_vsync + (1 + interval_fraction) * vsync_interval_;
 }
 
 }  // namespace content