Improve messaging for shared modules on chrome://extensions

List the dependent extensions under the shared module and change message
from generic policy message to be more specific for shared modules
to explain why the extension cannot be disabled or uninstalled.

BUG=393670

Review URL: https://codereview.chromium.org/403593002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@284010 0039d316-1c4b-4281-b951-d872f2087c98
7 files changed