Remove unnecessary threading concerns from VrMetricsHelper.

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 127 matching lines @@
   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;
 
   std::unique_ptr<UiInterface> html_interface_;
 
+  content::WebContents* main_contents_;
   std::unique_ptr<VrCompositor> content_compositor_;
-  content::WebContents* main_contents_;
+  content::WebContents* ui_contents_;
   std::unique_ptr<VrCompositor> ui_compositor_;
-  content::WebContents* ui_contents_;
+
   std::unique_ptr<VrWebContentsObserver> vr_web_contents_observer_;
 
   VrShellDelegate* delegate_ = nullptr;
   base::android::ScopedJavaGlobalRef<jobject> j_vr_shell_;
 
   std::unique_ptr<VrInputManager> content_input_manager_;
   std::unique_ptr<VrInputManager> ui_input_manager_;
-
-  scoped_refptr<VrMetricsHelper> metrics_helper_;
+  std::unique_ptr<VrMetricsHelper> metrics_helper_;
 
   scoped_refptr<base::SingleThreadTaskRunner> main_thread_task_runner_;
   std::unique_ptr<base::Thread> gl_thread_;
 
   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_