GitLab

This CL completes the refactoring of the ArcNavigationThrottle to be
app-platform agnostic by moving the callback run when the user responds
to the intent picker from ArcNavigationThrottle to
AppsNavigationThrottle. This will enable a future CL where the
AppsNavigationThrottle can insert non-ARC++ apps into the intent
picker, and then launch those apps if the user selects them.

There should be no functional changes from this CL. Two implementation
changes include:

1) the intent picker UI now returns an app-platform-generic CloseReason,
   and a boolean indicating if the user wanted to persist their choice.
   The AppsNavigationThrottle passes these to the ARC++ code, which
   interpolates them to the existing histogram buckets for metrics
   (which were formerly returned directly by the UI). This simplifies
   code in the UI layer, and moves responsibility for computing
   histogram values into the app-platform-specific code.

2) IntentPickerResponse is changed to be a OnceCallback, which removes
   some book-keeping in the UI layer for enforcing that it is only run
   once.

BUG=824598
TBR=sky@chromium.org

Change-Id: I1de4fd85c30e9ed09622ead11b709b9d6cdcfa98
Reviewed-on: https://chromium-review.googlesource.com/983197
Commit-Queue: Dominick Ng <dominickn@chromium.org>
Reviewed-by: Scott Violet <sky@chromium.org>
Reviewed-by: David Jacobo <djacobo@chromium.org>
Reviewed-by: Yusuke Sato <yusukes@chromium.org>
Cr-Commit-Position: refs/heads/master@{#548306}