track: Keep in cache the GSequenceIter so we get a faster acces to them
track: Keep in cache the GSequenceIter so we get a faster acces to them

pitivi/gst-editing-services,cfoch/gst-editing-services,cfoch/ges,cfoch/ges,cfoch/gst-editing-services,cfoch/gst-editing-services,cfoch/gst-editing-services,cfoch/ges,pitivi/gst-editing-services,pitivi/gst-editing-services,pitivi/gst-editing-services,cfoch/ges