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

chrome/browser/android/vr_shell/vr_shell.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_SHELL_H_
 #define CHROME_BROWSER_ANDROID_VR_SHELL_VR_SHELL_H_
 
 #include <jni.h>
 
 #include <memory>
@@ skipping 113 matching lines @@
   void QueueTask(base::Callback<void()>& callback);
 
   // Perform a UI action triggered by the javascript API.
   void DoUiAction(const UiAction action);
 
   void SetContentCssSize(float width, float height, float dpr);
   void SetUiCssSize(float width, float height, float dpr);
 
   void ContentFrameWasResized(bool width_changed);
 
-  void ForceExitVR();
+  void ForceExitVr();
 
  private:
   ~VrShell() override;
   void SetShowingOverscrollGlow(bool showing_glow);
 
   // content::WebContentsObserver implementation. All called on UI thread.
   void RenderViewHostChanged(content::RenderViewHost* old_host,
                              content::RenderViewHost* new_host) override;
   void MainFrameWasResized(bool width_changed) override;
   void WebContentsDestroyed() override;
@@ skipping 20 matching lines @@
   base::WeakPtrFactory<VrShell> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(VrShell);
 };
 
 bool RegisterVrShell(JNIEnv* env);
 
 }  // namespace vr_shell
 
 #endif  // CHROME_BROWSER_ANDROID_VR_SHELL_VR_SHELL_H_