GitLab

event->target() is different from
GetTopLevelWidgetForNativeView(event->target()))->GetNativeWindow()
for arc apps, but the same for chromeos apps.
Use native window of target's top level widget instead, then CanDrag
can get the correct value for arc apps, then we can drag the arc apps
from the top.

Bug: 847587
Change-Id: I9b0df4021b5872b823130450af43d93c0c97f6c8
Reviewed-on: https://chromium-review.googlesource.com/1157561Reviewed-by: Mitsuru Oshima <oshima@chromium.org>
Commit-Queue: Min Chen <minch@chromium.org>
Cr-Commit-Position: refs/heads/master@{#580931}