Check activation transfer state synchronously for postMessage sender.

Bug: 928838
Change-Id: I320d2669905f141910bb3bc490d79670c93a8e79
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1523962
Reviewed-by: Lan Wei <lanwei@chromium.org>
Commit-Queue: Mustaq Ahmed <mustaq@chromium.org>
Cr-Commit-Position: refs/heads/master@{#640849}
2 files changed