Allow VRDisplay to specify which frame the layer bounds should be updated at.

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/dom/TaskRunnerHelper.h"
@@ skipping 113 matching lines @@
   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;
 
-  void OnVSync(device::mojom::blink::VRPosePtr, double timeSeconds);
+  void OnVSync(device::mojom::blink::VRPosePtr,
+               double timeSeconds,
+               int16_t frameId);
   void OnVSyncProviderDisconnected();
   void ConnectVSyncProvider();
 
   ScriptedAnimationController& ensureScriptedAnimationController(Document*);
 
   Member<NavigatorVR> m_navigatorVR;
   unsigned m_displayId = 0;
   String m_displayName;
   bool m_isConnected = false;
   bool m_isPresenting = false;
   bool m_isValidDeviceForPresenting = true;
   Member<VRDisplayCapabilities> m_capabilities;
   Member<VRStageParameters> m_stageParameters;
   Member<VREyeParameters> m_eyeParametersLeft;
   Member<VREyeParameters> m_eyeParametersRight;
   device::mojom::blink::VRPosePtr m_framePose;
+  int16_t m_frameId;
   VRLayer m_layer;
   double m_depthNear = 0.01;
   double m_depthFar = 10000.0;
 
   void dispose();
 
   Timer<VRDisplay> m_fullscreenCheckTimer;
   String m_fullscreenOrigWidth;
   String m_fullscreenOrigHeight;
   gpu::gles2::GLES2Interface* m_contextGL = nullptr;
@@ skipping 30 matching lines @@
   ServiceInactive = 11,
   RequestDenied = 12,
   PresentationResultMax,  // Must be last member of enum.
 };
 
 void ReportPresentationResult(PresentationResult);
 
 }  // namespace blink
 
 #endif  // VRDisplay_h