app_shell: Fix resources.pak dependency issue

app_shell needs extensions-related feature JSON data, which is in
resources.pak. Without that file app_shell will build normally but crash
at runtime.

BUG=none
TEST=clean build of just the app_shell can launch normally
R=miket@chromium.org, tony@chromium.org

Review URL: https://codereview.chromium.org/131203008

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@244802 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 244802