Utilizing notifications.onShowSettings() event.

BUG=164227
TEST=Click at (i) icon in NC Settings for GN, make sure that the help URL opens.
R=robliao@chromium.org

Review URL: https://codereview.chromium.org/54643008

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@232488 0039d316-1c4b-4281-b951-d872f2087c98
2 files changed