Change method of activity tracking done in ActivityStatus.

Use the ability to track activity changes by registering a listener on
the application.

Also, this will manage the state of various activities on the java side.

BUG=286071

Review URL: https://chromiumcodereview.appspot.com/23522032

git-svn-id: http://src.chromium.org/chrome/trunk/src/testing@223437 4ff67af0-8c30-449e-8e8b-ad334ec8d88c