cc: Fix overlay damage tracking bug

content/browser/compositor/buffer_queue.cc

 // Copyright 2014 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/browser/compositor/buffer_queue.h"
 
 #include "content/browser/compositor/image_transport_factory.h"
 #include "content/browser/gpu/browser_gpu_memory_buffer_manager.h"
 #include "content/common/gpu/client/context_provider_command_buffer.h"
 #include "content/common/gpu/client/gl_helper.h"
@@ skipping 63 matching lines @@
     available_surfaces_[i].damage.Union(damage);
 
   for (std::deque<AllocatedSurface>::iterator it =
            in_flight_surfaces_.begin();
        it != in_flight_surfaces_.end();
        ++it)
     it->damage.Union(damage);
 }
 
 void BufferQueue::SwapBuffers(const gfx::Rect& damage) {
-  if (damage != gfx::Rect(size_)) {
+  if (!damage.IsEmpty() && damage != gfx::Rect(size_)) {
     // We must have a frame available to copy from.
     DCHECK(!in_flight_surfaces_.empty() || displayed_surface_.texture);
     unsigned int texture_id = !in_flight_surfaces_.empty()
                                   ? in_flight_surfaces_.back().texture
                                   : displayed_surface_.texture;
 
     CopyBufferDamage(current_surface_.texture, texture_id, damage,
                      current_surface_.damage);
   }
   UpdateBufferDamage(damage);
@@ skipping 149 matching lines @@
 BufferQueue::AllocatedSurface::AllocatedSurface(
     scoped_ptr<gfx::GpuMemoryBuffer> buffer,
     unsigned int texture,
     unsigned int image,
     const gfx::Rect& rect)
     : buffer(buffer.release()), texture(texture), image(image), damage(rect) {}
 
 BufferQueue::AllocatedSurface::~AllocatedSurface() {}
 
 }  // namespace content