Also some small additional changes as well:
+ Correct some :host selectors that were causing issues when Shadow DOM
was used instead of Shady DOM.
+ Two of the same revisions should not be shown in side-by-side view.
When two are specified via the url as /N..N/ redirect to /N/.
+ Added header to the diff view to give context and allow the user to
go back to the top-level change.
Feature: Issue 3676
Feature: Issue 3648
Feature: Issue 3649
Change-Id: Ib39bb7cb2eab26740f80971d4e00d579a2e08b0b
4c94478802