gpu: Cleanup class/struct forward declarations

gpu/command_buffer/service/context_state.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.
 
 // This file contains the ContextState class.
 
 #ifndef GPU_COMMAND_BUFFER_SERVICE_CONTEXT_STATE_H_
 #define GPU_COMMAND_BUFFER_SERVICE_CONTEXT_STATE_H_
 
 #include <memory>
 #include <vector>
 
 #include "base/logging.h"
 #include "gpu/command_buffer/service/gl_utils.h"
 #include "gpu/command_buffer/service/sampler_manager.h"
 #include "gpu/command_buffer/service/shader_manager.h"
 #include "gpu/command_buffer/service/texture_manager.h"
 #include "gpu/command_buffer/service/vertex_array_manager.h"
 #include "gpu/command_buffer/service/vertex_attrib_manager.h"
 #include "gpu/gpu_export.h"
 
 namespace gpu {
 namespace gles2 {
 
 class Buffer;
 class ErrorState;
 class ErrorStateClient;
 class FeatureInfo;
-class Framebuffer;
 class IndexedBufferBindingHost;
 class Logger;
 class Program;
 class Renderbuffer;
 class TransformFeedback;
 
 // State associated with each texture unit.
 struct GPU_EXPORT TextureUnit {
   TextureUnit();
   TextureUnit(const TextureUnit& other);
@@ skipping 326 matching lines @@
   GLfloat line_width_max_ = 1.0f;
 
   FeatureInfo* feature_info_;
   std::unique_ptr<ErrorState> error_state_;
 };
 
 }  // namespace gles2
 }  // namespace gpu
 
 #endif  // GPU_COMMAND_BUFFER_SERVICE_CONTEXT_STATE_H_