chrome: Eliminate BrowserWindowTesting interface once and for all.
This interface/abstract class was views only, implemented only by
BrowserView and used only within browser tests in
chrome/browser/ui/views.
To do what it is doing there were already other methods that could
provide the pointers the tests needed, so we changed them use those
other methods like going through BrowserView directly as we do
everywhere else.
This is the last patch from a series that started first in
https://chromium.googlesource.com/chromium/src/+/
80667a2e8e2b563efb7e935a44c54d5729cbeb35
and
https://chromium.googlesource.com/chromium/src/+/
8451cc1a50896771d5819cc9fe563a2b8cf2ca45.
BUG=None
TEST=browser_tests
R=sky@chromium.org
Review URL: https://codereview.chromium.org/
832783002
Cr-Commit-Position: refs/heads/master@{#309929}