Bug 967022 - Fix Gingerbread progressbar animation bustage. r=rnewman
Bug 983350 - Part 1: Standardize on Constants.USER_AGENT.
Bug 983350 - Part 2: Add new USER_AGENT strings.
Bug 983350 - Part 3: Add ResourceDelegate.getUserAgent.
Bug 983350 - Part 4: Add User-Agent header tests.