[Android]: Hide add-to-homescreen app menu item when WebAPK is installed

If the web page being shown has a related Web APK installed on the
phone, rather than saying 'Add to Homescreen' the menu item now says
'Open {app_name}'. (ex. 'Open Telegram').

For a more on-depth discussion on this please see the attached bug.

BUG=668258

Review-Url: https://codereview.chromium.org/2707993003
Cr-Commit-Position: refs/heads/master@{#453997}
10 files changed