Bug 1194037 part 2 - Make WillRefresh no longer call FlushAnimations; r=dholbert

In order to support ticking animations from their timeline we want to separate
the following two methods:

CommonAnimationManager::WillRefresh - responsible for responding to refresh
  driver ticks by updating timing information and posting the necessary
  pending restyles. This is the functionality we will eventually move to
  Animation.

CommonAnimationManager::FlushAnimations - responsible simply for posting
  pending restyles.

Currently, WillRefresh calls FlushAnimations. This patch separates the two by
copying the necessary functionality into WillRefresh. Later in this patch series
we will further separate the two by removing duplicate functionality from
FlushAnimations.

layout/style/AnimationCommon.cpp

@@ -452,7 +452,14 @@ CommonAnimationManager::WillRefresh(TimeStamp aTime)
     return;
   }
 
-  FlushAnimations(Can_Throttle);
+  nsAutoAnimationMutationBatch mb(mPresContext->Document());
+
+  for (AnimationCollection* collection = mElementCollections.getFirst();
+       collection; collection = collection->getNext()) {
+    collection->Tick();
+  }
+
+  MaybeStartOrStopObservingRefreshDriver();
 }
 
 #ifdef DEBUG