Fix WebVR does not properly stop presenting if requestPresent rejects.

third_party/WebKit/Source/modules/vr/VRDisplay.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 VRDisplay_h
 #define VRDisplay_h
 
 #include "core/dom/Document.h"
 #include "core/dom/FrameRequestCallback.h"
 #include "core/events/EventTarget.h"
@@ skipping 104 matching lines @@
 
   VRController* controller();
 
  private:
   void onFullscreenCheck(TimerBase*);
   void onPresentComplete(bool);
 
   void onConnected();
   void onDisconnected();
 
+  void stopPresenting();
+
   void OnPresentChange();
 
   // VRDisplayClient
   void OnChanged(device::mojom::blink::VRDisplayInfoPtr) override;
   void OnExitPresent() override;
   void OnBlur() override;
   void OnFocus() override;
   void OnActivate(device::mojom::blink::VRDisplayEventReason) override;
   void OnDeactivate(device::mojom::blink::VRDisplayEventReason) override;
 
@@ skipping 65 matching lines @@
   RequestDenied = 12,
   FullscreenNotEnabled = 13,
   PresentationResultMax,  // Must be last member of enum.
 };
 
 void ReportPresentationResult(PresentationResult);
 
 }  // namespace blink
 
 #endif  // VRDisplay_h