gpu: Fix corrupted state due to virtual MakeCurrent race.

gpu/command_buffer/service/gl_state_restorer_impl.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 GLStateRestorerImpl class.
 
 #ifndef GPU_COMMAND_BUFFER_SERVICE_GL_STATE_RESTORER_IMPL_H_
 #define GPU_COMMAND_BUFFER_SERVICE_GL_STATE_RESTORER_IMPL_H_
 
 #include "base/compiler_specific.h"
 #include "base/memory/weak_ptr.h"
 #include "gpu/gpu_export.h"
 #include "ui/gl/gl_state_restorer.h"
 
 namespace gpu {
 namespace gles2 {
 class GLES2Decoder;
 }
 
 // This class implements a GLStateRestorer that forwards to a GLES2Decoder.
 class GPU_EXPORT GLStateRestorerImpl : public gfx::GLStateRestorer {
  public:
    explicit GLStateRestorerImpl(base::WeakPtr<gles2::GLES2Decoder> decoder);
    virtual ~GLStateRestorerImpl();
 
+   virtual bool IsInitialized() OVERRIDE;
    virtual void RestoreState() OVERRIDE;
    virtual void RestoreAllTextureUnitBindings() OVERRIDE;
    virtual void RestoreFramebufferBindings() OVERRIDE;
 
  private:
    base::WeakPtr<gles2::GLES2Decoder> decoder_;
 
    DISALLOW_COPY_AND_ASSIGN(GLStateRestorerImpl);
 };
 
 }  // namespace gpu
 
 #endif  // GPU_COMMAND_BUFFER_SERVICE_GL_STATE_RESTORER_IMPL_H_