Allow FlushSyncs to short circuit

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.
 
 // 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 308 matching lines @@
 // textures.
 IPC_SYNC_MESSAGE_ROUTED2_1(GpuCommandBufferMsg_SetParent,
                            int32 /* parent_route_id */,
                            uint32 /* parent_texture_id */,
                            bool /* result */)
 
 // Get the current state of the command buffer.
 IPC_SYNC_MESSAGE_ROUTED0_1(GpuCommandBufferMsg_GetState,
                            gpu::CommandBuffer::State /* state */)
 
-// 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_ROUTED3_1(GpuCommandBufferMsg_Flush,
-                           int32 /* put_offset */,
-                           int32 /* last_known_get */,
-                           uint32 /* flush_count */,
+// Get the current state of the command buffer, as fast as possible.
+IPC_SYNC_MESSAGE_ROUTED0_1(GpuCommandBufferMsg_GetStateFast,
                            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_ROUTED2(GpuCommandBufferMsg_AsyncFlush,
                     int32 /* put_offset */,
                     uint32 /* flush_count */)
 
 // Asynchronously process any commands known to the GPU process. This is only
@@ skipping 164 matching lines @@
 
 // Confirm decoder has been reset.
 IPC_MESSAGE_ROUTED0(AcceleratedVideoDecoderHostMsg_ResetDone)
 
 // 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 */