aura/ash: Misc nits.

Some test related cleanups, e.g. add ToString() for EXPECT_EQ on gfx::
geometry types, add additional expections to clarify the test, reset
some states (and update subsequent expectations accordingly) to make
the tests more readable, etc. Also a couple of nits in the code.

BUG=none
R=jamescook@chromium.org

Review URL: https://codereview.chromium.org/137383002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@244597 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 244597