Overhaul handling tab data updates

 Bug: 2127502, 3191165
 Pushed some state tracking to the tab for URL, title, favicon,
 and lock status. This allowed me to remove many duplicate methods
 of updating that data, preventing the UI from getting out of sync
 with the web view.

Change-Id: I995caa98068ad03ca37710207b5ab57bb9d801ab
12 files changed