WebVR: Defer GetVSync calls until the current frame is submitted.

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 129 matching lines @@
                device::mojom::blink::VRVSyncProvider::Status);
   void ConnectVSyncProvider();
   void OnVSyncConnectionError();
 
   bool FocusedOrPresenting();
 
   ScriptedAnimationController& EnsureScriptedAnimationController(Document*);
   void ProcessScheduledAnimations(double timestamp);
   void ProcessScheduledWindowAnimations(double timestamp);
 
+  // In order to help the VR device with scheduling, never request a new VSync
+  // until the current frame is either submitted or abandoned. If vrDisplay.rAF
+  // is called earlier, defer the GetVSync until vrDisplay.submitFrame is
+  // called. If the rAF callback exits without submitting a frame, call it at
+  // that time.
+  void RequestVSync();
+
   Member<NavigatorVR> navigator_vr_;
   unsigned display_id_ = 0;
   String display_name_;
   bool is_connected_ = false;
   bool is_presenting_ = false;
   bool is_valid_device_for_presenting_ = true;
   Member<VRDisplayCapabilities> capabilities_;
   Member<VRStageParameters> stage_parameters_;
   Member<VREyeParameters> eye_parameters_left_;
   Member<VREyeParameters> eye_parameters_right_;
@@ skipping 18 matching lines @@
   Member<WebGLRenderingContextBase> rendering_context_;
 
   // Used to keep the image alive until the next frame if using
   // waitForPreviousTransferToFinish.
   RefPtr<Image> previous_image_;
 
   Member<ScriptedAnimationController> scripted_animation_controller_;
   bool pending_vrdisplay_raf_ = false;
   bool pending_vsync_ = false;
   bool in_animation_frame_ = false;
+  bool did_submit_this_frame_ = false;
   bool in_display_activate_ = false;
   bool display_blurred_ = false;
   double timebase_ = -1;
   bool pending_previous_frame_render_ = false;
   bool pending_submit_frame_ = false;
   bool v_sync_connection_failed_ = false;
   bool pending_present_request_ = false;
 
   device::mojom::blink::VRDisplayPtr display_;
 
@@ skipping 23 matching lines @@
   kRequestDenied = 12,
   kFullscreenNotEnabled = 13,
   kPresentationResultMax,  // Must be last member of enum.
 };
 
 void ReportPresentationResult(PresentationResult);
 
 }  // namespace blink
 
 #endif  // VRDisplay_h