App button click exits WebVR presentation.

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 128 matching lines @@
 
   // Perform a UI action triggered by the javascript API.
   void DoUiAction(const UiAction action,
                   const base::DictionaryValue* arguments);
 
   void SetContentCssSize(float width, float height, float dpr);
 
   void ContentFrameWasResized(bool width_changed);
 
   void ForceExitVr();
+  void ExitPresent();
 
   void ProcessContentGesture(std::unique_ptr<blink::WebInputEvent> event);
   void SubmitControllerModel(std::unique_ptr<VrControllerModel> model);
 
   // device::GvrGamepadDataProvider implementation.
   void UpdateGamepadData(device::GvrGamepadData) override;
   void RegisterGamepadDataFetcher(device::GvrGamepadDataFetcher*) override;
 
  private:
   ~VrShell() override;
@@ skipping 61 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_