Add OnDisplaysInitialized to DisplayController::Observer

this is a place for actions when displays are initialized after startup.

BUG=None

Review URL: https://codereview.chromium.org/199323003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@257302 0039d316-1c4b-4281-b951-d872f2087c98
12 files changed