GitLab

Add close check so that sharesheet can't close if it's already
in the process of closing.

Bug: 1153284
Change-Id: I1279240e2ceb9c7769ab96244d8aa3d3393aec11
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2570914
Auto-Submit: Melissa Zhang <melzhang@chromium.org>
Commit-Queue: Dominick Ng <dominickn@chromium.org>
Reviewed-by: Dominick Ng <dominickn@chromium.org>
Cr-Commit-Position: refs/heads/master@{#833517}