Encode frame number in pixel data for pose sync

device/vr/vr_service.mojom

Index: device/vr/vr_service.mojom
diff --git a/device/vr/vr_service.mojom b/device/vr/vr_service.mojom
index 0894f23facc79abd8f519ae66a7a4deea5fa7633..447f95d5adfac1862d9281cae204e4237eb96e35 100644
--- a/device/vr/vr_service.mojom
+++ b/device/vr/vr_service.mojom
@@ -13,7 +13,8 @@ struct VRFieldOfView {
 };
 
 // A display's position, orientation, velocity, and acceleration state at the
-// given timestamp.
+// given timestamp. The poseNum is a sequential ID that's incremented on

[mthiesse, 2016/10/04 21:19:17]

Again, I think frameIndex is less confusing. The frame index this pose applies
to.

[klausw, 2016/10/04 23:08:14]

Renamed to poseIndex.

+// each distinct getPose result, it may wrap around for long sessions.
 struct VRPose {
   double timestamp;
   array<float, 4>? orientation;
@@ -22,6 +23,7 @@ struct VRPose {
   array<float, 3>? linearVelocity;
   array<float, 3>? angularAcceleration;
   array<float, 3>? linearAcceleration;
+  uint32 poseNum;

[dcheng, 2016/10/04 23:17:53]

Nit: can we move the newly added comment here, so it's next to the thing it
defines?

[klausw, 2016/10/04 23:56:42]

Done.

 };
 
 struct VRDisplayCapabilities {