Don't update extension app on navigate if it doesnt' have a launch url.
The extension app is usually updated on navigations so that the app
icon shown in the windows task bar is correct. This shouldn't be done
if the extension associated with the browser doesn't have a valid
launch url.
This change only affects how the new bookmark apps operate. Prior to
the new bookmark apps system, the extension app is never updated on
navigations.
BUG=440670
Review URL: https://codereview.chromium.org/
788113004
Cr-Commit-Position: refs/heads/master@{#307679}