GitLab

BUG=331872
TEST=Visual
 Dock one browser window - should take all vertical space.
 Dock two browser windows - should reach to top / bottom of the docked area.
TEST=ash_unittests --gtest_filter=*Dock*

Review URL: https://codereview.chromium.org/101383004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@243236 0039d316-1c4b-4281-b951-d872f2087c98