GitLab

As is, OpaqueBrowserFrameView is untestable due to its
dependencies. This patch separates out all the layout and sizing logic
into a LayoutManager subclass, makes OpaqueBrowserFrameView use that,
and then adds tests for the new LayoutManager.

Note that I've deliberately made as few cleanups to the layout logic as
possible. The point is to get this code under test before I start more
radical changes.

BUG=281788

Review URL: https://chromiumcodereview.appspot.com/23531006

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@220683 0039d316-1c4b-4281-b951-d872f2087c98