Reviewed by Martin Robinson.

        check USE(GSTREAMER) instead of ENABLE(VIDEO) in gstreamer/ files
        https://bugs.webkit.org/show_bug.cgi?id=46717

        Define WTF_USE_GSTREAMER if configure found the gstreamer
        development files and add the macro in the gcc command-line if needed.

        * GNUmakefile.am:
        * configure.ac:

WebCore:

        Reviewed by Martin Robinson.

        check USE(GSTREAMER) instead of ENABLE(VIDEO) in gstreamer/ files
        https://bugs.webkit.org/show_bug.cgi?id=46717

        Guard the gstreamer/ files with USE(GSTREAMER), which is more
        explicit than ENABLE(VIDEO).

        * GNUmakefile.am: Define WTF_USE_GSTREAMER only if GStreamer
        support is enabled.
        * platform/graphics/gstreamer/DataSourceGStreamer.cpp:
        * platform/graphics/gstreamer/DataSourceGStreamer.h:
        * platform/graphics/gstreamer/GOwnPtrGStreamer.cpp:
        * platform/graphics/gstreamer/...