Bug 550426 - Fix browser_animation_animated_properties_delayed.js. r=dbaron

MozReview-Commit-ID: 6HyIM06pZfi

--HG--
extra : rebase_source : d68d8deee6c9f45459900ec14b3424a3770d3caf

devtools/client/animationinspector/test/browser_animation_animated_properties_displayed.js

@@ -9,7 +9,8 @@
 
 const EXPECTED_PROPERTIES = [
   "background-color",
-  "background-position",
+  "background-position-x",
+  "background-position-y",
   "background-size",
   "border-bottom-left-radius",
   "border-bottom-right-radius",