Add launch app button to CrostiniPackageNotification

When we finish installing a deb package from the UI, check if any
icons were added by the installation. If exactly one icon was added,
show an "Open App" button that allows the user to launch that app.

Bug: 864766
Change-Id: I8e2f03658a945f71aea5f1d1689b0a0dcfd548ee
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1652384
Commit-Queue: Fergus Dall <sidereal@google.com>
Reviewed-by: Joel Hockey <joelhockey@chromium.org>
Cr-Commit-Position: refs/heads/master@{#673626}
7 files changed