Rework FlushSync to return early if commands have been processed since the last update

content/common/gpu/gpu_messages.h

 // Copyright (c) 2011 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 <vector>
 #include <string>
 
 
 #include "base/shared_memory.h"
 #include "content/common/common_param_traits.h"
@@ skipping 323 matching lines @@
 // Get the current state of the command buffer.
 IPC_SYNC_MESSAGE_ROUTED0_1(GpuCommandBufferMsg_GetState,
                            gpu::CommandBuffer::State /* state */)
 
 // Get the current state of the command buffer asynchronously. State is
 // returned via UpdateState message.
 IPC_MESSAGE_ROUTED0(GpuCommandBufferMsg_AsyncGetState)
 
 // Synchronize the put and get offsets of both processes. Caller passes its
 // current put offset. Current state (including get offset) is returned.
-IPC_SYNC_MESSAGE_ROUTED1_1(GpuCommandBufferMsg_Flush,
+IPC_SYNC_MESSAGE_ROUTED2_1(GpuCommandBufferMsg_Flush,
                            int32 /* put_offset */,
+                           int32 /* last_known_get */,
                            gpu::CommandBuffer::State /* state */)
 
 // Asynchronously synchronize the put and get offsets of both processes.
 // Caller passes its current put offset. Current state (including get offset)
 // is returned via an UpdateState message.
 IPC_MESSAGE_ROUTED1(GpuCommandBufferMsg_AsyncFlush,
                     int32 /* put_offset */)
 
 // Return the current state of the command buffer following a request via
 // an AsyncGetState or AsyncFlush message. (This message is sent from the
@@ skipping 237 matching lines @@
 
 // Confirm decoder has been aborted.
 IPC_MESSAGE_ROUTED0(AcceleratedVideoDecoderHostMsg_AbortDone)
 
 // Decoder has faced end of stream marker in the stream.
 IPC_MESSAGE_ROUTED0(AcceleratedVideoDecoderHostMsg_EndOfStream)
 
 // Video decoder has encountered an error.
 IPC_MESSAGE_ROUTED1(AcceleratedVideoDecoderHostMsg_ErrorNotification,
                     uint32) /* Error ID */