GitLab

Add an InstanceRegistry pointer to ExtensionApps, to add the
instance to the InstanceRegistry when launching apps.

BUG=1011235

Change-Id: I85aea523ecd5e1ea68810bcc8e7e364d1798b5a1
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1913286
Commit-Queue: Nancy Wang <nancylingwang@chromium.org>
Reviewed-by: Dominick Ng <dominickn@chromium.org>
Cr-Commit-Position: refs/heads/master@{#715599}