--- a/layout/base/RestyleManager.cpp
+++ b/layout/base/RestyleManager.cpp
@@ -64,16 +64,17 @@ RestyleManager::RestyleManager(nsPresCon
   , mRebuildAllStyleData(false)
   , mObservingRefreshDriver(false)
   , mInStyleRefresh(false)
   , mSkipAnimationRules(false)
   , mPostAnimationRestyles(false)
   , mIsProcessingAnimationStyleChange(false)
   , mHoverGeneration(0)
   , mRebuildAllExtraHint(nsChangeHint(0))
+  , mRebuildAllRestyleHint(nsRestyleHint(0))
   , mLastUpdateForThrottledAnimations(aPresContext->RefreshDriver()->
                                         MostRecentRefresh())
   , mAnimationGeneration(0)
   , mReframingStyleContexts(nullptr)
   , mPendingRestyles(ELEMENT_HAS_PENDING_RESTYLE |
                      ELEMENT_IS_POTENTIAL_RESTYLE_ROOT)
   , mPendingAnimationRestyles(ELEMENT_HAS_PENDING_ANIMATION_RESTYLE |
                               ELEMENT_IS_POTENTIAL_ANIMATION_RESTYLE_ROOT)
@@ -1404,25 +1405,28 @@ RestyleManager::RestyleForRemove(Element
       if (content == aFollowingSibling) {
         reachedFollowingSibling = true;
       }
     }
   }
 }
 
 void
-RestyleManager::RebuildAllStyleData(nsChangeHint aExtraHint)
+RestyleManager::RebuildAllStyleData(nsChangeHint aExtraHint,
+                                    nsRestyleHint aRestyleHint)
 {
   NS_ASSERTION(!(aExtraHint & nsChangeHint_ReconstructFrame),
                "Should not reconstruct the root of the frame tree.  "
                "Use ReconstructDocElementHierarchy instead.");
 
   mRebuildAllStyleData = false;
   NS_UpdateHint(aExtraHint, mRebuildAllExtraHint);
+  aRestyleHint |= mRebuildAllRestyleHint;
   mRebuildAllExtraHint = nsChangeHint(0);
+  mRebuildAllRestyleHint = nsRestyleHint(0);
 
   nsIPresShell* presShell = mPresContext->GetPresShell();
   if (!presShell || !presShell->GetRootFrame())
     return;
 
   // Make sure that the viewmanager will outlive the presshell
   nsRefPtr<nsViewManager> vm = presShell->GetViewManager();
 
@@ -1443,23 +1447,17 @@ RestyleManager::RebuildAllStyleData(nsCh
 
   // 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, eRestyle_Subtree);
+  DoRebuildAllStyleData(mPendingRestyles, aExtraHint, aRestyleHint);
 
   mPostAnimationRestyles = false;
   mSkipAnimationRules = false;
 #ifdef DEBUG
   mIsProcessingRestyles = false;
 #endif
 
   // Make sure that we process any pending animation restyles from the
@@ -1584,17 +1582,17 @@ RestyleManager::ProcessPendingRestyles()
   NS_POSTCONDITION(mPendingRestyles.Count() == oldPendingRestyleCount,
                    "We should not have posted new non-animation restyles while "
                    "processing animation restyles");
 
   if (mRebuildAllStyleData) {
     // We probably wasted a lot of work up above, but this seems safest
     // and it should be rarely used.
     // This might add us as a refresh observer again; that's ok.
-    RebuildAllStyleData(nsChangeHint(0));
+    RebuildAllStyleData(nsChangeHint(0), nsRestyleHint(0));
   }
 }
 
 void
 RestyleManager::BeginProcessingRestyles()
 {
   // Make sure to not rebuild quote or counter lists while we're
   // processing restyles
@@ -1694,16 +1692,18 @@ void
 RestyleManager::PostRebuildAllStyleDataEvent(nsChangeHint aExtraHint)
 {
   NS_ASSERTION(!(aExtraHint & nsChangeHint_ReconstructFrame),
                "Should not reconstruct the root of the frame tree.  "
                "Use ReconstructDocElementHierarchy instead.");
 
   mRebuildAllStyleData = true;
   NS_UpdateHint(mRebuildAllExtraHint, aExtraHint);
+  // FIXME: pass through from callers
+  mRebuildAllRestyleHint = eRestyle_Subtree;
 
   // Get a restyle event posted if necessary
   PostRestyleEventInternal(false);
 }
 
 #ifdef DEBUG
 static void
 DumpContext(nsIFrame* aFrame, nsStyleContext* aContext)

--- a/layout/base/RestyleManager.h
+++ b/layout/base/RestyleManager.h
@@ -300,17 +300,27 @@ public:
   bool ThrottledAnimationStyleIsUpToDate() const {
     return mLastUpdateForThrottledAnimations ==
              mPresContext->RefreshDriver()->MostRecentRefresh();
   }
 
   // Rebuilds all style data by throwing out the old rule tree and
   // building a new one, and additionally applying aExtraHint (which
   // must not contain nsChangeHint_ReconstructFrame) to the root frame.
-  void RebuildAllStyleData(nsChangeHint aExtraHint);
+  //
+  // aRestyleHint says which restyle hint to use for the computation;
+  // the only sensible values to use are eRestyle_Subtree (which says
+  // that the rebuild must run selector matching) and nsRestyleHint(0)
+  // (which says that rerunning selector matching is not required.  (The
+  // method adds eRestyle_ForceDescendants internally, and including it
+  // in the restyle hint is harmless; some callers (e.g.,
+  // nsPresContext::MediaFeatureValuesChanged) might do this for their
+  // own reasons.)
+  void RebuildAllStyleData(nsChangeHint aExtraHint,
+                           nsRestyleHint aRestyleHint);
 
   // Helper that does part of the work of RebuildAllStyleData, shared by
   // RestyleElement for 'rem' handling.
   void DoRebuildAllStyleData(RestyleTracker& aRestyleTracker,
                              nsChangeHint aExtraHint,
                              nsRestyleHint aRestyleHint);
 
   // See PostRestyleEventCommon below.
@@ -457,16 +467,17 @@ private:
   // mSkipAnimationRules is also true.
   bool mPostAnimationRestyles : 1;
   // Whether we're currently in the animation phase of restyle
   // processing (to be eliminated in bug 960465)
   bool mIsProcessingAnimationStyleChange : 1;
 
   uint32_t mHoverGeneration;
   nsChangeHint mRebuildAllExtraHint;
+  nsRestyleHint mRebuildAllRestyleHint;
 
   mozilla::TimeStamp mLastUpdateForThrottledAnimations;
 
   OverflowChangedTracker mOverflowChangedTracker;
 
   // The total number of animation flushes by this frame constructor.
   // Used to keep the layer and animation manager in sync.
   uint64_t mAnimationGeneration;

--- a/layout/base/nsPresContext.cpp
+++ b/layout/base/nsPresContext.cpp
@@ -1859,17 +1859,18 @@ nsPresContext::RebuildAllStyleData(nsCha
     return;
   }
 
   mUsesRootEMUnits = false;
   mUsesViewportUnits = false;
   RebuildUserFontSet();
   RebuildCounterStyles();
 
-  RestyleManager()->RebuildAllStyleData(aExtraHint);
+  // FIXME: Pass through from callers
+  RestyleManager()->RebuildAllStyleData(aExtraHint, eRestyle_Subtree);
 }
 
 void
 nsPresContext::PostRebuildAllStyleDataEvent(nsChangeHint aExtraHint)
 {
   if (!mShell) {
     // We must have been torn down. Nothing to do here.
     return;