commit 6088355323ac15ee243051f88f94b065a8f975c7
author Wenzhao Zang <wzang@chromium.org> Wed Apr 11 02:26:13 2018
committer Commit Bot <commit-bot@chromium.org> Wed Apr 11 02:26:13 2018
tree 5f561742cd7151b201b308d2a3ca4aa48c54cb03
parent 5d969dd6c09fe37e89de502e16983274fa39567c

cros: Disable backdrop for wallpaper picker app in preview mode

The preview wallpaper is blocked by a black backdrop in tablet mode,
on the new wallpaper picker (see #3 of the bug).

There are basically two ways to disable it:

1) (Not used) Disable backdrop based on the extension id, but it
   requires creating a new field in |AppWindow::CreateParams|, and we
   may need to hard code the extension id in a "white list" or something
   similar.

2) (This CL) Notify backdrop controller when preview mode starts. The
   drawback of this approach is: backdrop controller has to assume that
   the active window is indeed the wallpaper picker (because it's not
   feasible to create an extension id <-> aura::Window map.) This should
   be OK because |wallpaper_window_state_manager| has been using active
   window as the wallpaper picker window for a long time.

Bug: 818075
Test: --new-wallpaper-picker --force-tablet-mode=touch_view
Change-Id: I12420b7ee83df32913820bf85038e2278f3940ac
Reviewed-on: https://chromium-review.googlesource.com/932911
Reviewed-by: Scott Violet <sky@chromium.org>
Reviewed-by: Mitsuru Oshima <oshima@chromium.org>
Reviewed-by: Xiaoqian Dai <xdai@chromium.org>
Commit-Queue: Wenzhao (Colin) Zang <wzang@chromium.org>
Cr-Commit-Position: refs/heads/master@{#549734}