Simplify plumbing pointer-events:none for a remote frame's surface layer

Rather than plumb this through several layers so that //content can set
the corresponding bit, just set it directly from Blink.

Bug: 841358
Change-Id: Id3fd32f75f07b5c8361220ee44402ce403e624c4
Reviewed-on: https://chromium-review.googlesource.com/1225931
Commit-Queue: Daniel Cheng <[email protected]>
Reviewed-by: Ken Buchanan <[email protected]>
Reviewed-by: Antoine Labour <[email protected]>
Cr-Commit-Position: refs/heads/master@{#592284}
20 files changed