GitLab

Since WebLayer was sending old_state for the constraint, a switch from
SHOWN to HIDDEN, as when entering fullscreen, could hit a DCHECK in
browser_controls_offset_manager.cc

I think some confusion arises from the re-use of a single enum for both
the _constraint_ and the _current state_. Code used the terms old_state
and new_state, when really the RenderFrameHost method expected a new
constraint and new desired state. The BOTH value in the context of a
constraint means unconstrained, and in the context of a state means
"don't change unless you have to to conform to the constraint".

Test: requestFullscreen on an element in weblayer shell doesn't cause
      the renderer to crash in debug

Bug: 1107647
Change-Id: I4f72e1144a9fc9a0cf0934b9640c660867c0d971
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2310652
Commit-Queue: Evan Stade <estade@chromium.org>
Reviewed-by: Scott Violet <sky@chromium.org>
Cr-Commit-Position: refs/heads/master@{#790603}