Bug 771042, part 3 - Enable the reftests/svg/smil/motion tests. r=birtles.

layout/reftests/svg/smil/reftest.list

@@ -14,6 +14,9 @@
 #   - Some more "anim-retarget" tests, with attributeType being changed/cleared.
 #     (after we've got support for SVG/SMIL animation of CSS properties)
 
+# animateMotion tests
+include motion/reftest.list
+
 # animation sort-order tests
 include sort/reftest.list