Implement WebVR presentation pausing for VR Shell Menu Mode

device/vr/android/gvr/gvr_device_provider.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 DEVICE_VR_ANDROID_GVR_DEVICE_PROVIDER_H
 #define DEVICE_VR_ANDROID_GVR_DEVICE_PROVIDER_H
 
 #include <memory>
 
 #include "base/macros.h"
 #include "base/single_thread_task_runner.h"
 #include "device/vr/vr_device.h"
 #include "device/vr/vr_device_provider.h"
 #include "device/vr/vr_export.h"
 
 namespace device {
 
 class GvrDelegate;
 class GvrDevice;
 class VRServiceImpl;
 
 class DEVICE_VR_EXPORT GvrDeviceProvider : public VRDeviceProvider {
  public:
   GvrDeviceProvider();
-  ~GvrDeviceProvider() override;
 
   void GetDevices(std::vector<VRDevice*>* devices) override;
   void Initialize() override;
 
-  // Called from GvrDevice
+  // Called from GvrDevice.
   bool RequestPresent();
   void ExitPresent();
 
-  // Called from GvrDelegate
+  // Called from GvrDelegate. May be called from any thread.
   void OnGvrDelegateReady(GvrDelegate* delegate);
   void OnGvrDelegateRemoved();
 
+  // May be called from any thread. This function is likely to be called from
+  // an arbitrary GL thread handling GVR controller updates.
+  void OnDisplayBlur();
+
+  // May be called from any thread. This function is likely to be called from
+  // an arbitrary GL thread handling GVR controller updates.
+  void OnDisplayFocus();
+
  private:
+  ~GvrDeviceProvider() override;
+
   void GvrDelegateReady(GvrDelegate* delegate);
   void GvrDelegateRemoved();
 
   std::unique_ptr<GvrDevice> vr_device_;
 
   scoped_refptr<base::SingleThreadTaskRunner> main_thread_task_runner_;
 
   DISALLOW_COPY_AND_ASSIGN(GvrDeviceProvider);
 };
 
 }  // namespace device
 
 #endif  // DEVICE_VR_ANDROID_GVR_DEVICE_PROVIDER_H