--- a/dom/animation/KeyframeEffect.cpp
+++ b/dom/animation/KeyframeEffect.cpp
@@ -163,28 +163,21 @@ KeyframeEffectReadOnly::NotifyAnimationT
         effectSet->MarkCascadeNeedsUpdate();
       }
     }
     mInEffectOnLastAnimationTimingUpdate = inEffect;
   }
 
   // Request restyle if necessary.
   //
-  // Bug 1235002: We should skip requesting a restyle when mProperties is empty.
-  // However, currently we don't properly encapsulate mProperties so we can't
-  // detect when it changes. As a result, if we skip requesting restyles when
-  // mProperties is empty and we play an animation and *then* add properties to
-  // it (as we currently do when building CSS animations), we will fail to
-  // request a restyle at all. Since animations without properties are rare, we
-  // currently just request the restyle regardless of whether mProperties is
-  // empty or not.
-  //
   // Bug 1216843: When we implement iteration composite modes, we need to
   // also detect if the current iteration has changed.
-  if (mAnimation && GetComputedTiming().mProgress != mProgressOnLastCompose) {
+  if (mAnimation &&
+      !mProperties.IsEmpty() &&
+      GetComputedTiming().mProgress != mProgressOnLastCompose) {
     EffectCompositor::RestyleType restyleType =
       CanThrottle() ?
       EffectCompositor::RestyleType::Throttled :
       EffectCompositor::RestyleType::Standard;
     RequestRestyle(restyleType);
   }
 
   // If we're no longer "in effect", our ComposeStyle method will never be

--- a/dom/animation/test/chrome/test_restyles.html
+++ b/dom/animation/test/chrome/test_restyles.html
@@ -437,12 +437,42 @@ waitForAllPaints(function() {
 
     ok(animation.isRunningOnCompositor,
        'Opacity script animations restored from "display: none" should be ' +
        'run on the compositor');
 
     yield ensureElementRemoval(div);
   });
 
+  add_task(function* restyling_for_empty_keyframes() {
+    var div = addDiv(null);
+    var animation = div.animate({ }, 100 * MS_PER_SEC);
+
+    yield animation.ready;
+    var markers = yield observeStyling(5);
+
+    is(markers.length, 0,
+       'Animations with no keyframes should not cause restyles');
+
+    animation.effect.setFrames({ backgroundColor: ['red', 'blue'] });
+    markers = yield observeStyling(5);
+
+    // There are 5 eRestyle_CSSAnimations and 1 eRestyle_CSSTransitions.
+    // 1 eRestyle_CSSTransitions comes from
+    // EffectCompositor::UpdateCascadeResults.
+    ok(markers.length == 6,
+       'Setting valid keyframes should cause regular animation restyles to ' +
+       'occur');
+
+    animation.effect.setFrames({ });
+    markers = yield observeStyling(5);
+
+    is(markers.length, 1,
+       'Setting an empty set of keyframes should trigger a single restyle ' +
+       'to remove the previous animated style');
+
+    yield ensureElementRemoval(div);
+  });
+
 });
 
 </script>
 </body>