I found a memory leak while running Cheese, which uses clutter-gst. The Valgrind trace is:

==947== 473 (40 direct, 433 indirect) bytes in 1 blocks are definitely lost in l
oss record 25,806 of 27,371
==947==    at 0x4A0645D: malloc (in /usr/lib64/valgrind/vgpreload_memcheck-amd64
-linux.so)
==947==    by 0x922EF40: g_malloc (gmem.c:102)
==947==    by 0x92449DD: g_slice_alloc (gslice.c:1014)
==947==    by 0x91FEA34: g_array_sized_new (garray.c:198)
==947==    by 0x5948837: gst_caps_new_empty (gstcaps.c:224)
==947==    by 0x594ADCA: gst_caps_intersect_full (gstcaps.c:1488)
==947==    by 0x3B4957C4: clutter_gst_auto_video_sink_query (clutter-gst-auto-video-sink.c:455)
==947==    by 0x5973379: gst_pad_query (gstpad.c:3506)
==947==    by 0x59A5C35: gst_pad_query_accept_caps (gstutils.c:2847)
==947==    by 0x56E6989: gst_base_transform_setcaps (gstbasetransform.c:1189)
==947==    by 0x56E7FC4: gst_base_transform_sink_eventfunc (gstbasetransform.c:1860)
==947==    by 0x596C1AA: gst_pad_send_event_unchecked (gstpad.c:5036)
==947==    by 0x596C993: gst_pad_push_event_unchecked (gstpad.c:4732)
==947==    by 0x596CE07: push_sticky (gstpad.c:3365)
==947==    by 0x596B1F1: events_foreach (gstpad.c:533)
==947==    by 0x5975697: gst_pad_push_event (gstpad.c:3421)
==947==    by 0x56E708C: gst_base_transform_setcaps (gstcompat.h:55)
==947==    by 0x56E7FC4: gst_base_transform_sink_eventfunc (gstbasetransform.c:1860)
==947==    by 0x596C1AA: gst_pad_send_event_unchecked (gstpad.c:5036)
==947==    by 0x596C993: gst_pad_push_event_unchecked (gstpad.c:4732)