Remove unnecessary uses of aura::Env::GetDispatcher

Avoid using aura::Env::GetDispatcher() as the dispatcher for new instances of
base::RunLoop()s, since for both Windows and X11, it's the same as the message-pump.

This patch also removes some non-aura views code, and some unnecessary USE_AURA ifdefs.

R=darin@chromium.org, sky@chromium.org

Review URL: https://codereview.chromium.org/154203002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@249105 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 249105