--- a/layout/base/RestyleManager.cpp
+++ b/layout/base/RestyleManager.cpp
@@ -59,16 +59,18 @@ FrameTagToString(const nsIFrame* aFrame)
 }
 #endif
 
 RestyleManager::RestyleManager(nsPresContext* aPresContext)
   : mPresContext(aPresContext)
   , mRebuildAllStyleData(false)
   , mObservingRefreshDriver(false)
   , mInStyleRefresh(false)
+  , mSkipAnimationRules(false)
+  , mPostAnimationRestyles(false)
   , mHoverGeneration(0)
   , mRebuildAllExtraHint(nsChangeHint(0))
   , mLastUpdateForThrottledAnimations(aPresContext->RefreshDriver()->
                                         MostRecentRefresh())
   , mAnimationGeneration(0)
   , mReframingStyleContexts(nullptr)
   , mPendingRestyles(ELEMENT_HAS_PENDING_RESTYLE |
                      ELEMENT_IS_POTENTIAL_RESTYLE_ROOT)
@@ -1434,26 +1436,35 @@ RestyleManager::RebuildAllStyleData(nsCh
   nsAutoScriptBlocker scriptBlocker;
 
   MOZ_ASSERT(!mIsProcessingRestyles, "Nesting calls to processing restyles");
 #ifdef DEBUG
   mIsProcessingRestyles = true;
 #endif
   mPresContext->SetProcessingRestyles(true);
 
+  // Until we get rid of these phases in bug 960465, we need to skip
+  // animation restyles during the non-animation phase, and post
+  // animation restyles so that we restyle those elements again in the
+  // animation phase.
+  mSkipAnimationRules = true;
+  mPostAnimationRestyles = true;
+
   // FIXME (bug 1047928): Many of the callers probably don't need
   // eRestyle_Subtree because they're changing things that affect data
   // computation rather than selector matching; we could have a restyle
   // hint passed in, and substantially improve the performance of things
   // like pref changes and the restyling that we do for downloadable
   // font loads.
   DoRebuildAllStyleData(mPendingRestyles, aExtraHint,
                         nsRestyleHint(eRestyle_Subtree |
                                       eRestyle_ForceDescendants));
 
+  mPostAnimationRestyles = false;
+  mSkipAnimationRules = false;
 #ifdef DEBUG
   mIsProcessingRestyles = false;
 #endif
   mPresContext->SetProcessingRestyles(false);
 
   // Make sure that we process any pending animation restyles from the
   // above style change.  Note that we can *almost* implement the above
   // by just posting a style change -- except we really need to restyle
@@ -1534,18 +1545,28 @@ RestyleManager::ProcessPendingRestyles()
   // if any style changes we cause trigger transitions, we have the
   // correct old style for starting the transition.
   if (nsLayoutUtils::AreAsyncAnimationsEnabled() &&
       mPendingRestyles.Count() > 0) {
     ++mAnimationGeneration;
     UpdateOnlyAnimationStyles();
   }
 
+  // Until we get rid of these phases in bug 960465, we need to skip
+  // animation restyles during the non-animation phase, and post
+  // animation restyles so that we restyle those elements again in the
+  // animation phase.
+  mSkipAnimationRules = true;
+  mPostAnimationRestyles = true;
+
   mPendingRestyles.ProcessRestyles();
 
+  mPostAnimationRestyles = false;
+  mSkipAnimationRules = false;
+
 #ifdef DEBUG
   uint32_t oldPendingRestyleCount = mPendingRestyles.Count();
 #endif
 
   // ...and then process animation restyles.  This needs to happen
   // second because we need to start animations that resulted from the
   // first set of restyles (e.g., CSS transitions with negative
   // transition-delay), and because we need to immediately

--- a/layout/base/RestyleManager.h
+++ b/layout/base/RestyleManager.h
@@ -87,16 +87,32 @@ public:
   // Get an integer that increments every time there is a style change
   // as a result of a change to the :hover content state.
   uint32_t GetHoverGeneration() const { return mHoverGeneration; }
 
   // Get a counter that increments on every style change, that we use to
   // track whether off-main-thread animations are up-to-date.
   uint64_t GetAnimationGeneration() const { return mAnimationGeneration; }
 
+  // Whether rule matching should skip styles associated with animation
+  bool SkipAnimationRules() const {
+    MOZ_ASSERT(mSkipAnimationRules || !mPostAnimationRestyles,
+               "inconsistent state");
+    return mSkipAnimationRules;
+  }
+
+  // Whether rule matching should post animation restyles when it skips
+  // styles associated with animation.  Only true when
+  // SkipAnimationRules() is also true.
+  bool PostAnimationRestyles() const {
+    MOZ_ASSERT(mSkipAnimationRules || !mPostAnimationRestyles,
+               "inconsistent state");
+    return mPostAnimationRestyles;
+  }
+
   /**
    * Reparent the style contexts of this frame subtree.  The parent frame of
    * aFrame must be changed to the new parent before this function is called;
    * the new parent style context will be automatically computed based on the
    * new position in the frame tree.
    *
    * @param aFrame the root of the subtree to reparent.  Must not be null.
    */
@@ -422,16 +438,23 @@ private:
 private:
   nsPresContext* mPresContext; // weak, disconnected in Disconnect
 
   bool mRebuildAllStyleData : 1;
   // True if we're already waiting for a refresh notification
   bool mObservingRefreshDriver : 1;
   // True if we're in the middle of a nsRefreshDriver refresh
   bool mInStyleRefresh : 1;
+  // Whether rule matching should skip styles associated with animation
+  bool mSkipAnimationRules : 1;
+  // Whether rule matching should post animation restyles when it skips
+  // styles associated with animation.  Only true when
+  // mSkipAnimationRules is also true.
+  bool mPostAnimationRestyles : 1;
+
   uint32_t mHoverGeneration;
   nsChangeHint mRebuildAllExtraHint;
 
   mozilla::TimeStamp mLastUpdateForThrottledAnimations;
 
   OverflowChangedTracker mOverflowChangedTracker;
 
   // The total number of animation flushes by this frame constructor.