Separate tab switcher mode toolbar from browsing mode toolbar

Create a new TabSwitcherModeTTPhone view that is lazily inflated the
first time the user enters the tab switcher (except when Duet is
enabled, which doesn't have a top toolbar in the tab switcher).

Follow-up CLs will focus on applying MVC to the tab switcher toolbar and
improving code sharing between the tab switcher toolbar and duet.

BUG=897294

Change-Id: Ie930aaf281a8fbb805f784e500d505ea3e6db057
Reviewed-on: https://chromium-review.googlesource.com/c/1371069
Reviewed-by: Matthew Jones <mdjones@chromium.org>
Reviewed-by: Ted Choc <tedchoc@chromium.org>
Commit-Queue: Theresa <twellington@chromium.org>
Cr-Commit-Position: refs/heads/master@{#616837}
22 files changed