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This CL moves the remaining client of the NOTIFICATION_GOOGLE_URL_UPDATED
notification to instead register a callback with GoogleURLTracker and
eliminates the notification. It also migrate the GoogleURLTracker unittest from
listening for the notification to listening for the callback.

BUG=373261,373237
TBR=thakis

Review URL: https://codereview.chromium.org/284343003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@271313 0039d316-1c4b-4281-b951-d872f2087c98