GitLab

When BrowserRootView is being destroyed, we shouldn't call callbacks from
DropTarget. It might be already destroyed.

Bug: 1001942
Change-Id: Iddecc9334d814f9154d44ff32473c5fa167b3b23
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1844001
Commit-Queue: Peter Kasting <pkasting@chromium.org>
Reviewed-by: Peter Kasting <pkasting@chromium.org>
Cr-Commit-Position: refs/heads/master@{#703352}