GPU: Adding sync points for cross-channel synchronization

gpu/ipc/command_buffer_proxy.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.
 
 #ifndef GPU_IPC_COMMAND_BUFFER_PROXY_H_
 #define GPU_IPC_COMMAND_BUFFER_PROXY_H_
 #pragma once
 
 #include <string>
 
@@ skipping 19 matching lines @@
   // Invoke the task when the channel has been flushed. Takes care of deleting
   // the task whether the echo succeeds or not.
   virtual bool Echo(const base::Closure& callback) = 0;
 
   // Sends an IPC message with the new state of surface visibility.
   virtual bool SetSurfaceVisible(bool visible) = 0;
 
   virtual bool DiscardBackbuffer() = 0;
   virtual bool EnsureBackbuffer() = 0;
 
+  // Inserts a sync point, returning its ID. This is handled on the IO thread of
+  // the GPU process, and so should be relatively fast, but its effect is
+  // ordered wrt other messages (in particular, Flush). Sync point IDs are
+  // global and can be used for cross-channel synchronization.
+  virtual uint32 InsertSyncPoint() = 0;
+
+  // Makes this command buffer wait on a sync point. This command buffer will be
+  // unscheduled until the command buffer that inserted that sync point reaches
+  // it, or gets destroyed.
+  virtual void WaitSyncPoint(uint32) = 0;
+
   // Register a callback to invoke whenever we recieve a new memory allocation.
   virtual void SetMemoryAllocationChangedCallback(
       const base::Callback<void(const GpuMemoryAllocationForRenderer&)>&
           callback) = 0;
 
   // Reparent a command buffer. TODO(apatrick): going forward, the notion of
   // the parent / child relationship between command buffers is going away in
   // favor of the notion of surfaces that can be drawn to in one command buffer
   // and bound as a texture in any other.
   virtual bool SetParent(CommandBufferProxy* parent_command_buffer,
                          uint32 parent_texture_id) = 0;
 
   virtual void SetChannelErrorCallback(const base::Closure& callback) = 0;
 
   // Set a task that will be invoked the next time the window becomes invalid
   // and needs to be repainted. Takes ownership of task.
   virtual void SetNotifyRepaintTask(const base::Closure& callback) = 0;
 
   virtual void SetOnConsoleMessageCallback(
       const GpuConsoleMessageCallback& callback) = 0;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(CommandBufferProxy);
 };
 
 #endif  // GPU_IPC_COMMAND_BUFFER_PROXY_H_