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

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.
+// 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;
   float rightDegrees;
 };
 
 // A display's position, orientation, velocity, and acceleration state at the
 // given timestamp.
 struct VRPose {
   double timestamp;
   array<float, 4>? orientation;
   array<float, 3>? position;
   array<float, 3>? angularVelocity;
   array<float, 3>? linearVelocity;
   array<float, 3>? angularAcceleration;
   array<float, 3>? linearAcceleration;
-  // The poseIndex is a sequential ID that's incremented on each distinct
-  // getPose result, it may wrap around for long sessions.
-  uint32 poseIndex;
 };
 
 struct VRDisplayCapabilities {
   bool hasOrientation;
   bool hasPosition;
   bool hasExternalDisplay;
   bool canPresent;
 };
 
 // Information about the optical properties for an eye in a VRDisplay.
@@ skipping 26 matching lines @@
   float height;
 };
 
 enum VRDisplayEventReason {
   NONE = 0,
   NAVIGATION = 1,
   MOUNTED = 2,
   UNMOUNTED = 3
 };
 
-// TODO(shaobo.yan@intel.com) : Add comments to describe these interfaces about how to use and where they live.
+// TODO(shaobo.yan@intel.com) : Add comments to describe these interfaces about
+// how to use and where they live.
 interface VRService {
-  // TODO(shaobo.yan@intel.com) : Use a factory function which took a VRServiceClient
-  // so we would never have a half-initialized VRService.
+  // TODO(shaobo.yan@intel.com) : Use a factory function which took a
+  // VRServiceClient so we would never have a half-initialized VRService.
   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);
+  OnDisplayConnected(VRDisplay display, VRDisplayClient& request,
+                     VRDisplayInfo displayInfo);
 };
 
 interface VRDisplay {
   ResetPose();
 
   RequestPresent(bool secureOrigin) => (bool success);
   ExitPresent();
   SubmitFrame(VRPose? pose);
-  UpdateLayerBounds(VRLayerBounds leftBounds, VRLayerBounds rightBounds);
+  UpdateLayerBounds(int16 frameId, VRLayerBounds leftBounds,
+                    VRLayerBounds rightBounds);
   GetVRVSyncProvider(VRVSyncProvider& request);
 };
 
 interface VRVSyncProvider {
-  GetVSync() => (VRPose? pose, double timeSeconds);
+  // The frameId maps a VSync to a frame arriving from the compositor. IDs will
+  // be reused after the frame arrives from the compositor. Negative IDs imply
+  // no mapping.
+  GetVSync() => (VRPose? pose, double timeSeconds, int16 frameId);
 };
 
 interface VRDisplayClient {
   OnChanged(VRDisplayInfo display);
   OnExitPresent();
   OnBlur();
   OnFocus();
   OnActivate(VRDisplayEventReason reason);
   OnDeactivate(VRDisplayEventReason reason);
 };