CHECK that messages are not forwarded from RenderView to RenderWidget.

Widget messages should be directly sent to RenderWidgets rather than
relying on fallback from RenderView. This adds a CHECK() to enforce that
and validate that nothing too insane is happening in the wild. Assuming
nothing goes wrong, the CHECK() will be removed in a week or so.

Bug: 419087
Change-Id: I0aa21020931fa907db64a71a3e8d189e7ffa1f8c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1733028
Commit-Queue: Daniel Cheng <dcheng@chromium.org>
Reviewed-by: Alex Moshchuk <alexmos@chromium.org>
Reviewed-by: Erik Chen <erikchen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#683864}
4 files changed