In the configure.ac PKG_CHECK_MODULES call for gstreamer the action-if-not-found we have is to set $have_gstreamer to "no". The consequence is that in this case the build will fail.
So if HTML5 media is enabled at configure time and if the pkg-config gstreamer check fails the configure script should error out, which is the default action-if-not-found of PKG_CHECK_MODULES.
Created attachment 76030 [details]
Comment on attachment 76030 [details]
Committed r73600: <http://trac.webkit.org/changeset/73600>