Added method to synchronize command buffers within GpuControl.

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 <stddef.h>
 #include <stdint.h>
 
@@ skipping 68 matching lines @@
   // Sets a lock this will be held on every callback from the GPU
   // implementation. This lock must be set and must be held on every call into
   // 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;
 
+  // This command forces the server to the synchronized with the client by
+  // sending a synchronous IPC. Once this function returns, it is guaranteed
+  // that the server will have received any asynchronous commands previously
+  // sent by this command buffer. Note just that it is received does not
+  // necessarily mean that it has been processed. This is only relevant for
+  // out of process servers and will be treated as a NOP for in process
+  // command buffers.
+  virtual void SynchronizeCommandBuffer() = 0;

[piman, 2016/01/05 00:28:38]

Sorry for the bikeshed, but I would prefer a more descriptive name (because we
have many kind of synchronization, it's really unclear from the name what it
means).

How about: EnsureWorkVisible() ? When it returns all the previously flushed work
is visible by the service.

[David Yen, 2016/01/05 00:47:51]

Done.

+
   // 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.
   virtual CommandBufferNamespace GetNamespaceID() const = 0;
   virtual uint64_t GetCommandBufferID() const = 0;
   virtual int32_t GetExtraCommandBufferData() const = 0;
 
@@ skipping 19 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_