GitLab

When the iframe finishes resizing send a postMessage to the doodle
iframe letting it know the expansion has finished.

b/118340003

Change-Id: Ic974ca58f51882d932e8de10c5706990f8f462cd
Reviewed-on: https://chromium-review.googlesource.com/c/1323620Reviewed-by: Ramya Nagarajan <ramyan@chromium.org>
Commit-Queue: Kyle Milka <kmilka@chromium.org>
Cr-Commit-Position: refs/heads/master@{#607729}