Prevent browser crash resulting from misbehaving WebVR renderer requesting multiple VSyncs.

third_party/WebKit/Source/modules/vr/VRDisplay.h

Index: third_party/WebKit/Source/modules/vr/VRDisplay.h
diff --git a/third_party/WebKit/Source/modules/vr/VRDisplay.h b/third_party/WebKit/Source/modules/vr/VRDisplay.h
index 5e29e95c13de602b18e4fb0580a9a752d0e29c77..b35f831469c1917c222acb05dc8ea98b3704de9c 100644
--- a/third_party/WebKit/Source/modules/vr/VRDisplay.h
+++ b/third_party/WebKit/Source/modules/vr/VRDisplay.h
@@ -136,7 +136,8 @@ class VRDisplay final : public EventTargetWithInlineData,
 
   void OnVSync(device::mojom::blink::VRPosePtr,
                mojo::common::mojom::blink::TimeDeltaPtr,
-               int16_t frameId);
+               int16_t frameId,
+               device::mojom::blink::VRVSyncProvider::Error);
   void ConnectVSyncProvider();
 
   ScriptedAnimationController& ensureScriptedAnimationController(Document*);
@@ -171,6 +172,7 @@ class VRDisplay final : public EventTargetWithInlineData,
 
   Member<ScriptedAnimationController> m_scriptedAnimationController;
   bool m_pendingRaf = false;
+  bool m_pendingVsync = false;
   bool m_inAnimationFrame = false;
   bool m_displayBlurred = false;
   bool m_reenteredFullscreen = false;