Perform glReadPixels with PBOs in the gpu, if PBOs are available.

content/common/gpu/gpu_command_buffer_stub.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_COMMON_GPU_GPU_COMMAND_BUFFER_STUB_H_
 #define CONTENT_COMMON_GPU_GPU_COMMAND_BUFFER_STUB_H_
 
 #include <deque>
 #include <string>
 #include <vector>
@@ skipping 157 matching lines @@
   void OnSetSurfaceVisible(bool visible);
 
   void OnDiscardBackbuffer();
   void OnEnsureBackbuffer();
 
   void OnRetireSyncPoint(uint32 sync_point);
   bool OnWaitSyncPoint(uint32 sync_point);
   void OnSyncPointRetired();
   void OnSignalSyncPoint(uint32 sync_point, uint32 id);
   void OnSignalSyncPointAck(uint32 id);
+  void OnSignalQuery(uint32 query, uint32 id);
 
   void OnReceivedClientManagedMemoryStats(const GpuManagedMemoryStats& stats);
   void OnSetClientHasMemoryAllocationChangedCallback(bool has_callback);
 
   void OnCommandProcessed();
   void OnParseError();
   void OnSetLatencyInfo(const ui::LatencyInfo& latency_info);
 
   void ReportState();
 
@@ skipping 59 matching lines @@
   size_t active_url_hash_;
 
   size_t total_gpu_memory_;
 
   DISALLOW_COPY_AND_ASSIGN(GpuCommandBufferStub);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_COMMON_GPU_GPU_COMMAND_BUFFER_STUB_H_