Revert of Added an extra sync token field for extra command buffer identification.

gpu/command_buffer/client/gpu_control.h

 // 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.
 
 #ifndef GPU_COMMAND_BUFFER_CLIENT_GPU_CONTROL_H_
 #define GPU_COMMAND_BUFFER_CLIENT_GPU_CONTROL_H_
 
 #include <stdint.h>
 
 #include <vector>
@@ skipping 69 matching lines @@
   // the GPU implementation if it is to be used from multiple threads. This
   // may not be supported with all implementations.
   virtual void SetLock(base::Lock*) = 0;
 
   // Returns true if the channel to the Gpu is lost. When true, all contexts
   // should be considered as lost.
   virtual bool IsGpuChannelLost() = 0;
 
   // The namespace and command buffer ID forms a unique pair for all existing
   // GpuControl (on client) and matches for the corresponding command buffer
-  // (on server) in a single server process. The extra command buffer data can
-  // be used for extra identification purposes. One usage is to store some
-  // extra field to identify unverified sync tokens for the implementation of
-  // the CanWaitUnverifiedSyncToken() function.
+  // (on server) in a single server process.
   virtual CommandBufferNamespace GetNamespaceID() const = 0;
   virtual uint64_t GetCommandBufferID() const = 0;
-  virtual int32_t GetExtraCommandBufferData() const = 0;
 
   // Fence Syncs use release counters at a context level, these fence syncs
   // need to be flushed before they can be shared with other contexts across
   // channels. Subclasses should implement these functions and take care of
   // figuring out when a fence sync has been flushed. The difference between
   // IsFenceSyncFlushed and IsFenceSyncFlushReceived, one is testing is the
   // client has issued the flush, and the other is testing if the service
   // has received the flush.
   virtual uint64_t GenerateFenceSyncRelease() = 0;
   virtual bool IsFenceSyncRelease(uint64_t release) = 0;
@@ skipping 10 matching lines @@
   // be enqueued first so does not need to be flushed.
   virtual bool CanWaitUnverifiedSyncToken(const SyncToken* sync_token) = 0;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(GpuControl);
 };
 
 }  // namespace gpu
 
 #endif  // GPU_COMMAND_BUFFER_CLIENT_GPU_CONTROL_H_