WebVR: lock focus while presenting to presenting window
This CL is kept intentionally simple for merging back to M59 to fix the regression, but hides some complexity.
This won't violate the assumption of one VRDisplay having a VSync provider at a time because VrDisplayImpl::GetVRVSyncProvider drops requests from displays that aren't presenting while presentation is active.
However, if a non-presenting VrDisplay actually gets focus while a different VrDisplay is presenting (possibly from directing the controller click to a different display) then that non-presenting VrDisplay will fail to get a VSync provider even after presentation ends because its focused state won't change and the original request will have failed. This means that a page with multiple VrDisplays will under certain degenerate cases fail to resume magic window mode after presenting until the focus changes again.
BUG=710863
Review-Url: https://codereview.chromium.org/2859533003
Cr-Original-Commit-Position: refs/heads/master@{#469804}
Review-Url: https://codereview.chromium.org/2881233002 .
Cr-Commit-Position: refs/branch-heads/3071@{#560}
Cr-Branched-From: a106f0abbf69dad349d4aaf4bcc4f5d376dd2377-refs/heads/master@{#464641}
5 files changed
