[iOS] Use Browser in BrowserCoordinator

This CL adds an initializer for ChromeCoordinator that takes a Browser, and
has BrowserCoordinator use that initializer. Most of the other changes are
just making that new init unavailable in other ChromeCoordinator subclasses.

Change-Id: I28fee06fc259d7737d6327acb86bbdf25dfed2bf
Reviewed-on: https://chromium-review.googlesource.com/c/1421902
Commit-Queue: Mark Cogan <marq@chromium.org>
Reviewed-by: Rohit Rao <rohitrao@chromium.org>
Cr-Commit-Position: refs/heads/master@{#624585}
17 files changed