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diff --git a/gpu/command_buffer/common/command_buffer.h b/gpu/command_buffer/common/command_buffer.h
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+++ b/gpu/command_buffer/common/command_buffer.h
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+// Copyright (c) 2006-2008 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_COMMON_COMMAND_BUFFER_H_
+#define GPU_COMMAND_BUFFER_COMMON_COMMAND_BUFFER_H_
+
+#include "base/shared_memory.h"
+#include "base/task.h"
+
+namespace command_buffer {
+
+// Common interface for CommandBuffer implementations.
+class CommandBuffer {
+ public:
+  CommandBuffer() {
+  }
+
+  virtual ~CommandBuffer() {
+  }
+
+  // Initialize the command buffer with the given ring buffer. Takes ownership
+  // of ring buffer.
+  virtual bool Initialize(::base::SharedMemory* ring_buffer) = 0;
+
+  // Gets the shared memory ring buffer object for the command buffer.
+  virtual ::base::SharedMemory* GetRingBuffer() = 0;
+
+  virtual int32 GetSize() = 0;
+
+  // The writer calls this to update its put offset. This function returns the
+  // reader's most recent get offset. Does not return until after the put offset
+  // change callback has been invoked. Returns -1 if the put offset is invalid.
+  virtual int32 SyncOffsets(int32 put_offset) = 0;
+
+  // Returns the current get offset. This can be called from any thread.
+  virtual int32 GetGetOffset() = 0;
+
+  // Sets the current get offset. This can be called from any thread.
+  virtual void SetGetOffset(int32 get_offset) = 0;
+
+  // Returns the current put offset. This can be called from any thread.
+  virtual int32 GetPutOffset() = 0;
+
+  // Sets a callback that should be posted on another thread whenever the put
+  // offset is changed. The callback must not return until some progress has
+  // been made (unless the command buffer is empty), i.e. the
+  // get offset must have changed. It need not process the entire command
+  // buffer though. This allows concurrency between the writer and the reader
+  // while giving the writer a means of waiting for the reader to make some
+  // progress before attempting to write more to the command buffer. Avoiding
+  // the use of a synchronization primitive like a condition variable to
+  // synchronize reader and writer reduces the risk of deadlock.
+  // Takes ownership of callback. The callback is invoked on the plugin thread.
+  virtual void SetPutOffsetChangeCallback(Callback0::Type* callback) = 0;
+
+  // Create a shared memory transfer buffer and return a handle that uniquely
+  // identifies it or -1 on error.
+  virtual int32 CreateTransferBuffer(size_t size) = 0;
+
+  // Destroy a shared memory transfer buffer and recycle the handle.
+  virtual void DestroyTransferBuffer(int32 id) = 0;
+
+  // Get the shared memory associated with a handle.
+  virtual ::base::SharedMemory* GetTransferBuffer(int32 handle) = 0;
+
+  // Get the current token value. This is used for by the writer to defer
+  // changes to shared memory objects until the reader has reached a certain
+  // point in the command buffer. The reader is responsible for updating the
+  // token value, for example in response to an asynchronous set token command
+  // embedded in the command buffer. The default token value is zero.
+  virtual int32 GetToken() = 0;
+
+  // Allows the reader to update the current token value.
+  virtual void SetToken(int32 token) = 0;
+
+  // Get the current parse error and reset it to zero. Zero means no error. Non-
+  // zero means error. The default error status is zero.
+  virtual int32 ResetParseError() = 0;
+
+  // Allows the reader to set the current parse error.
+  virtual void SetParseError(int32 parse_error) = 0;
+
+  // Returns whether the command buffer is in the error state.
+  virtual bool GetErrorStatus() = 0;
+
+  // Allows the reader to set the error status. Once in an error state, the
+  // command buffer cannot recover and ceases to process commands.
+  virtual void RaiseErrorStatus() = 0;
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(CommandBuffer);
+};
+
+}  // namespace command_buffer
+
+#endif  // GPU_COMMAND_BUFFER_COMMON_COMMAND_BUFFER_H_