Adds views::corewm::WMState to install common state

I'm going to need to install a another singleton client for
transients. Rather than touch all places to explicitly set n clients
I'm creating Environment to centralize common setup and teardown.

BUG=none
TEST=none
R=ben@chromium.org

Review URL: https://codereview.chromium.org/105813013

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@242126 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 242126