GitLab

Creates InfobarManagerAppInterface to allow for retrieval of InfobarManager
state.

Bug: 987646
Change-Id: Ic518fe7ffaaeec27b08f6a3e4a37a12dc84387fd
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1914535
Commit-Queue: Chris Lu <thegreenfrog@chromium.org>
Reviewed-by: Eugene But <eugenebut@chromium.org>
Cr-Commit-Position: refs/heads/master@{#715898}