Use a per-frame task runner at GuestViewContainer

This CL switches task runners at several places from per-thread to
per-frame. The purpose of this change is to make it possible to freeze
tasks for bfcache.

We found an actual case that JavaScript is executed:
browser_tests --gtest_filter=WebViewScrollGuestContentBrowserPluginSpecificTest.OverscrollControllerSeesConsumedScrollsInGuest

Bug: 870606
Change-Id: I34d1cb8b94955798a896e741b76135dec6f8c031
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1530314
Reviewed-by: Alexander Timin <altimin@chromium.org>
Reviewed-by: Kevin McNee <mcnee@chromium.org>
Commit-Queue: Hajime Hoshi <hajimehoshi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#642360}
1 file changed