Fix some thread safety violations in device::GvrDelegate implementation.

chrome/browser/android/vr_shell/vr_compositor.h

 // Copyright 2016 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 CHROME_BROWSER_ANDROID_VR_SHELL_VR_COMPOSITOR_H_
 #define CHROME_BROWSER_ANDROID_VR_SHELL_VR_COMPOSITOR_H_
 
 #include <memory>
 
 #include "base/android/scoped_java_ref.h"
 #include "base/macros.h"
 #include "content/public/browser/android/compositor_client.h"
+#include "ui/gfx/geometry/size.h"
 
 typedef unsigned int SkColor;
 
 namespace cc {
 class Layer;
 }
 
 namespace content {
 class Compositor;
 class WebContents;
 }
 
 namespace ui {
 class WindowAndroid;
 }
 
 namespace vr_shell {
 
 class VrCompositor : public content::CompositorClient {
  public:
   VrCompositor(ui::WindowAndroid* window, bool is_transparent);
   ~VrCompositor() override;
 
   void SurfaceDestroyed();
-  void SetWindowBounds(int width, int height);
+  void SetWindowBounds(gfx::Size size);
+  gfx::Size GetWindowBounds() { return bounds_; }
   void SurfaceChanged(jobject surface);
   void SetLayer(content::WebContents* web_contents);
 
   // CompositorClient implementation:
   void UpdateLayerTreeHost() override;
   void OnSwapBuffersCompleted(int pending_swap_buffers) override;
 
  private:
   std::unique_ptr<content::Compositor> compositor_;
+  gfx::Size bounds_;
 
   cc::Layer* layer_ = nullptr;
   cc::Layer* layer_parent_ = nullptr;
   SkColor background_color_;
   bool transparent_;
 
   DISALLOW_COPY_AND_ASSIGN(VrCompositor);
 };
 
 }  // namespace vr_shell
 
 #endif  // CHROME_BROWSER_ANDROID_VR_SHELL_VR_COMPOSITOR_H_