Move DeviceMotionAndOrientation off Activity Context

- Get rid of WeakContext since it ties to the Activity and is only used in one place.
- Move DeviceMotionAndOrientation onto the Application context

BUG=341231

Review URL: https://codereview.chromium.org/167803002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@252629 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 252629