Fix text caret visibility after screen rotation on SingleProcessMash

There can be a race between the browser receiving window bounds updates
and the IME ensuring the text caret is visible.

* Repeat the text caret visibility request after virtual keyboard
  occluded bounds update. This is a no-op if the caret is already
  visible.
* Fix double-conversion of local bounds to screen bounds in chrome's
  receipt of occluded bounds from ash.
* Clarify variable names with coordinate system.

Bug: 937722

Change-Id: I0f49413ca63582469cf0a4b61cde69733c1841ab
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1504150
Reviewed-by: Xiyuan Xia <xiyuan@chromium.org>
Reviewed-by: Darren Shen <shend@chromium.org>
Commit-Queue: James Cook <jamescook@chromium.org>
Cr-Commit-Position: refs/heads/master@{#638308}
11 files changed