Adds button to VRShell menu mode, which lets the user manually exit WebVR presentation.

chrome/browser/android/vr_shell/vr_shell_delegate.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_DELEGATE_H_
 #define CHROME_BROWSER_ANDROID_VR_SHELL_VR_SHELL_DELEGATE_H_
 
 #include <jni.h>
 
 #include <memory>
@@ skipping 33 matching lines @@
                            const base::android::JavaParamRef<jobject>& obj,
                            jlong timebase_nanos,
                            jdouble interval_seconds);
   void OnPause(JNIEnv* env, const base::android::JavaParamRef<jobject>& obj);
   void OnResume(JNIEnv* env, const base::android::JavaParamRef<jobject>& obj);
   void Destroy(JNIEnv* env, const base::android::JavaParamRef<jobject>& obj);
   device::mojom::VRSubmitFrameClientPtr TakeSubmitFrameClient();
 
   device::GvrDeviceProvider* device_provider() { return device_provider_; }
 
+  // device::GvrDelegateProvider implementation.
+  void ExitWebVRPresent() override;
+
  private:
-  // device::GvrDelegateProvider implementation
+  // device::GvrDelegateProvider implementation.
   void SetDeviceProvider(device::GvrDeviceProvider* device_provider) override;
   void ClearDeviceProvider() override;
   void RequestWebVRPresent(device::mojom::VRSubmitFrameClientPtr submit_client,
                            const base::Callback<void(bool)>& callback) override;
-  void ExitWebVRPresent() override;
   device::GvrDelegate* GetDelegate() override;
   void SetListeningForActivate(bool listening) override;
 
   void CreateNonPresentingDelegate();
 
   std::unique_ptr<NonPresentingGvrDelegate> non_presenting_delegate_;
   base::android::ScopedJavaGlobalRef<jobject> j_vr_shell_delegate_;
   device::GvrDeviceProvider* device_provider_ = nullptr;
   device::GvrDelegate* delegate_ = nullptr;
   base::Callback<void(bool)> present_callback_;
   int64_t timebase_nanos_ = 0;
   double interval_seconds_ = 0;
   device::mojom::VRSubmitFrameClientPtr submit_client_;
 
   DISALLOW_COPY_AND_ASSIGN(VrShellDelegate);
 };
 
 bool RegisterVrShellDelegate(JNIEnv* env);
 
 }  // namespace vr_shell
 
 #endif  // CHROME_BROWSER_ANDROID_VR_SHELL_VR_SHELL_DELEGATE_H_