Bug 847287 patch 10 - Only call CheckNeedsRefresh if we might have changed mNeedsRefreshes, to make it cheaper to call EnsureStyleRuleFor more than once per refresh cycle. r=birtles

This saves some extra work that we don't need to do.

I want to do this here since patch 9 introduces a new call to
EnsureStyleRuleFor.

layout/style/AnimationCommon.cpp

@@ -825,9 +825,9 @@ AnimationPlayerCollection::EnsureStyleRuleFor(TimeStamp aRefreshTime,
       mPlayers[playerIdx]->ComposeStyle(mStyleRule, properties,
                                         mNeedsRefreshes);
     }
-  }
 
-  mManager->CheckNeedsRefresh();
+    mManager->CheckNeedsRefresh();
+  }
 }
 
 bool