Remove Sync GetPose VRService call, implement VRVSyncProvider

device/vr/vr_service.mojom

 // Copyright 2015 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.
 
 module device.mojom;
 
 // A field of view, given by 4 degrees describing the view from a center point.
 struct VRFieldOfView {
   float upDegrees;
   float downDegrees;
   float leftDegrees;
@@ skipping 66 matching lines @@
   SetClient(VRServiceClient client) => (uint32 numberOfConnectedDevices);
   // Inform the service that the page is listening for vrdisplayactivate events.
   SetListeningForActivate(bool listening);
 };
 
 interface VRServiceClient {
   OnDisplayConnected(VRDisplay display, VRDisplayClient& request, VRDisplayInfo displayInfo);
 };
 
 interface VRDisplay {
-  [Sync]
-  GetPose() => (VRPose? pose);
   ResetPose();
 
   RequestPresent(bool secureOrigin) => (bool success);
   ExitPresent();
   SubmitFrame(VRPose? pose);
   UpdateLayerBounds(VRLayerBounds leftBounds, VRLayerBounds rightBounds);
 };
 
+interface VRVSyncProviderClient {
+  // VRVSyncProviders should ensure the callback from OnVSync is run before sending another OnVSync
+  // to avoid having multiple VSyncs queue up in the case of a slow client.
+  OnVSync(VRPose? pose, double time_seconds) => ();
+};
+
 interface VRDisplayClient {
   OnChanged(VRDisplayInfo display);
   OnExitPresent();
   OnBlur();
   OnFocus();
   OnActivate(VRDisplayEventReason reason);
   OnDeactivate(VRDisplayEventReason reason);
+  OnVRVsyncProviderReady() => (VRVSyncProviderClient client);
 };