[ChromeOS] Implement new progress bar mock.

BUG=chromium-os:8465
TEST=Verify progress bar has new look now per chromium-os:8465.

Review URL: http://codereview.chromium.org/4236001

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@64924 0039d316-1c4b-4281-b951-d872f2087c98