GitLab

1) Add back button support :)
- Adds a OverviewModeController that also gives the owner the APIs to
show and hide the Overview.
- Adds an internal implementation in ChromeTabbedActivity that will hold
on to an overridable Controller and use that for all signaling. Every
component gets the Container class and never changes it.
- Extend the API for RecyclerView to support not animating hide and show
- Have GridMediator implement controller and the Coordinator hand that
off with a public API when needed.
- Have the TabbedActivity explicitly own the Grid component and override
the Controller.
- Replace all calls related with Controller using LayoutManager with
related Controller calls.

2) Makes sure the grid always shows the current tab when shown.

3) Disables swiping from toolbar to show the StackLayout and
ToolbarSwipeLayout. (I will try to see if there is a path to enabling
ToolbarSwipeLayout without adding a ton, but for now this is the most
"elegant solution")

BUG=934564

Change-Id: Ic778d2e2c158ba5e089f22d829f321f42e0e7684
Reviewed-on: https://chromium-review.googlesource.com/c/1484734
Commit-Queue: Yusuf Ozuysal <yusufo@chromium.org>
Reviewed-by: Ted Choc <tedchoc@chromium.org>
Cr-Commit-Position: refs/heads/master@{#635755}