desktop-pwas: Create shortcuts for placeholder apps

InstallFinalizer does not create shortcuts automatically so we have
to create them in BookmarkAppInstallation task when installing a place-
holder app.

Also add a bool to control whether a desktop shortcut will be created
in addition to the applications menu one, since policy doesn't always
create desktop shortcuts.

Bug: 955926
Change-Id: I059257c5aa154caf336400e50cb6cb96f5c2ba1e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1580683
Reviewed-by: Alexey Baskakov <loyso@chromium.org>
Commit-Queue: Giovanni Ortuño Urquidi <ortuno@chromium.org>
Cr-Commit-Position: refs/heads/master@{#653507}
10 files changed