V2: Implement reparenting, bounds and visibility change notifications, and write more tests.

TBR=sky@chromium.org
BUG=none

Review URL: https://codereview.chromium.org/25757007

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@226847 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 226847