Reland "WebVR: Update VRDisplay.GetFrameData to follow the current spec."

This is a reland of 14020f57ee8a8bc8cce58c3fc694cfc00c2d0467
Original change's description:
> WebVR: Update VRDisplay.GetFrameData to follow the current spec.
> 
> The WebVR 1.1 spec was updated to clarify the behavior of getFrameData.
> Now, GetFrameData should return false unless called within a
> VRDisplay.requestAnimationFrame callback.
> 
> BUG=736023
> 
> Change-Id: I14d9442a016817a78232ed7b1e71956c8dac614a
> Reviewed-on: https://chromium-review.googlesource.com/578188
> Reviewed-by: Brandon Jones <bajones@chromium.org>
> Commit-Queue: Bill Orr <billorr@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#487970}

Bug: 736023
Change-Id: Ib2020621f70152f7399899d91db283c90df7026f
Reviewed-on: https://chromium-review.googlesource.com/604667
Reviewed-by: Brandon Jones <bajones@chromium.org>
Commit-Queue: Bill Orr <billorr@chromium.org>
Commit-Queue: Brandon Jones <bajones@chromium.org>
Cr-Commit-Position: refs/heads/master@{#492493}
2 files changed