GitLab

We are adding a nullcheck before the callback because callers
may call ShowBubble with NullCallback.

Bug: 1142706
Change-Id: I2d3c1376b036057a2e5890e20a10f6478d5c7075
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2589139
Commit-Queue: Melissa Zhang <melzhang@chromium.org>
Auto-Submit: Melissa Zhang <melzhang@chromium.org>
Reviewed-by: Dominick Ng <dominickn@chromium.org>
Cr-Commit-Position: refs/heads/master@{#836527}