Add ability for running packaged app to badge their taskbar icon.

This is only implemented on Windows with this patch.

BUG=311878

Review URL: https://codereview.chromium.org/140883018

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@250086 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 250086
Hide the shortcut overlay in the app launcher for windowed streamlined hosted apps.

This CL makes hosted apps that run as windows get their shortcut overlay
hidden.  In order for the app list to get updated on pref change, the
ExtensionAppModelBuilder now listens to ExtensionPrefs changes and
updates the ExtensionAppItem icons if necessary.

This CL also re-enables the drop shadow on hosted apps in the app launcher.
This was necessary because switching an app from windowed to tabbed would cause
the icon the jump around as the shadow was added and removed.

BUG=318607

Review URL: https://codereview.chromium.org/145123004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@250087 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 250087