Add IPC allowing GPU process to tell browser process to temporarily drop a front buffer.

content/common/gpu/gpu_messages.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.
 
 // Multiply-included message file, hence no include guard here, but see below
 // for a much smaller-than-usual include guard section.
 
 #include <vector>
 #include <string>
 
@@ skipping 233 matching lines @@
 // should cause the browser to redraw the compositor's contents.
 IPC_MESSAGE_CONTROL1(GpuHostMsg_AcceleratedSurfacePostSubBuffer,
                      GpuHostMsg_AcceleratedSurfacePostSubBuffer_Params)
 
 // Tells the browser to release whatever resources are associated with
 // the given surface. The browser must send an ACK once this operation
 // is complete.
 IPC_MESSAGE_CONTROL1(GpuHostMsg_AcceleratedSurfaceRelease,
                      GpuHostMsg_AcceleratedSurfaceRelease_Params)
 
+// Tells the browser to release resources for the given surface until the next
+// time swap buffers or post sub buffer is sent.
+IPC_MESSAGE_CONTROL1(GpuHostMsg_AcceleratedSurfaceSuspend,
+                     int32 /* surface_id */)
+
 //------------------------------------------------------------------------------
 // GPU Channel Messages
 // These are messages from a renderer process to the GPU process.
 
 // Initialize a channel between a renderer process and a GPU process. The
 // renderer passes its process handle to the GPU process, which gives gives the
 // GPU process the ability to map handles from the renderer process. This must
 // be the first message sent on a newly connected channel.
 IPC_MESSAGE_CONTROL1(GpuChannelMsg_Initialize,
                      base::ProcessHandle /* renderer_process_for_gpu */)
@@ skipping 202 matching lines @@
 
 // Confirm decoder has been flushed.
 IPC_MESSAGE_ROUTED0(AcceleratedVideoDecoderHostMsg_FlushDone)
 
 // Confirm decoder has been reset.
 IPC_MESSAGE_ROUTED0(AcceleratedVideoDecoderHostMsg_ResetDone)
 
 // Video decoder has encountered an error.
 IPC_MESSAGE_ROUTED1(AcceleratedVideoDecoderHostMsg_ErrorNotification,
                     uint32) /* Error ID */