--- a/dom/xbl/nsBindingManager.cpp
+++ b/dom/xbl/nsBindingManager.cpp
@@ -704,99 +704,72 @@ nsBindingManager::WalkRules(nsIStyleRule
 
   // If "content" is non-null that means we cut off inheritance at some point
   // in the loop.
   *aCutOffInheritance = (content != nullptr);
 
   return NS_OK;
 }
 
-typedef nsTHashtable<nsPtrHashKey<nsIStyleRuleProcessor> > RuleProcessorSet;
+void
+nsBindingManager::EnumerateBoundContentBindings(
+  const BoundContentBindingCallback& aCallback) const
+{
+  if (!mBoundContentSet) {
+    return;
+  }
 
-static RuleProcessorSet*
-GetContentSetRuleProcessors(nsTHashtable<nsRefPtrHashKey<nsIContent>>* aContentSet)
-{
-  RuleProcessorSet* set = nullptr;
-
-  for (auto iter = aContentSet->Iter(); !iter.Done(); iter.Next()) {
+  for (auto iter = mBoundContentSet->Iter(); !iter.Done(); iter.Next()) {
     nsIContent* boundContent = iter.Get()->GetKey();
-    for (nsXBLBinding* binding = boundContent->GetXBLBinding(); binding;
+    for (nsXBLBinding* binding = boundContent->GetXBLBinding();
+         binding;
          binding = binding->GetBaseBinding()) {
-      nsIStyleRuleProcessor* ruleProc =
-        binding->PrototypeBinding()->GetRuleProcessor();
-      if (ruleProc) {
-        if (!set) {
-          set = new RuleProcessorSet;
-        }
-        set->PutEntry(ruleProc);
-      }
+      aCallback(binding);
     }
   }
-
-  return set;
 }
 
 void
 nsBindingManager::WalkAllRules(nsIStyleRuleProcessor::EnumFunc aFunc,
                                ElementDependentRuleProcessorData* aData)
 {
-  if (!mBoundContentSet) {
-    return;
-  }
-
-  nsAutoPtr<RuleProcessorSet> set;
-  set = GetContentSetRuleProcessors(mBoundContentSet);
-  if (!set) {
-    return;
-  }
-
-  for (auto iter = set->Iter(); !iter.Done(); iter.Next()) {
-    nsIStyleRuleProcessor* ruleProcessor = iter.Get()->GetKey();
-    (*(aFunc))(ruleProcessor, aData);
-  }
+  EnumerateBoundContentBindings([=](nsXBLBinding* aBinding) {
+    nsIStyleRuleProcessor* ruleProcessor =
+      aBinding->PrototypeBinding()->GetRuleProcessor();
+    if (ruleProcessor) {
+      (*(aFunc))(ruleProcessor, aData);
+    }
+  });
 }
 
 nsresult
 nsBindingManager::MediumFeaturesChanged(nsPresContext* aPresContext,
                                         bool* aRulesChanged)
 {
   *aRulesChanged = false;
-  if (!mBoundContentSet) {
-    return NS_OK;
-  }
+  RefPtr<nsPresContext> presContext = aPresContext;
 
-  nsAutoPtr<RuleProcessorSet> set;
-  set = GetContentSetRuleProcessors(mBoundContentSet);
-  if (!set) {
-    return NS_OK;
-  }
-
-  for (auto iter = set->Iter(); !iter.Done(); iter.Next()) {
-    nsIStyleRuleProcessor* ruleProcessor = iter.Get()->GetKey();
-    bool thisChanged = ruleProcessor->MediumFeaturesChanged(aPresContext);
-    *aRulesChanged = *aRulesChanged || thisChanged;
-  }
+  EnumerateBoundContentBindings([=](nsXBLBinding* aBinding) {
+    nsIStyleRuleProcessor* ruleProcessor =
+      aBinding->PrototypeBinding()->GetRuleProcessor();
+    if (ruleProcessor) {
+      bool thisChanged = ruleProcessor->MediumFeaturesChanged(presContext);
+      *aRulesChanged = *aRulesChanged || thisChanged;
+    }
+  });
 
   return NS_OK;
 }
 
 void
 nsBindingManager::AppendAllSheets(nsTArray<StyleSheet*>& aArray)
 {
-  if (!mBoundContentSet) {
-    return;
-  }
-
-  for (auto iter = mBoundContentSet->Iter(); !iter.Done(); iter.Next()) {
-    nsIContent* boundContent = iter.Get()->GetKey();
-    for (nsXBLBinding* binding = boundContent->GetXBLBinding(); binding;
-         binding = binding->GetBaseBinding()) {
-      binding->PrototypeBinding()->AppendStyleSheetsTo(aArray);
-    }
-  }
+  EnumerateBoundContentBindings([&aArray](nsXBLBinding* aBinding) {
+    aBinding->PrototypeBinding()->AppendStyleSheetsTo(aArray);
+  });
 }
 
 static void
 InsertAppendedContent(XBLChildrenElement* aPoint,
                       nsIContent* aFirstNewContent)
 {
   int32_t insertionIndex;
   if (nsIContent* prevSibling = aFirstNewContent->GetPreviousSibling()) {

--- a/dom/xbl/nsBindingManager.h
+++ b/dom/xbl/nsBindingManager.h
@@ -188,16 +188,22 @@ protected:
   void DoProcessAttachedQueue();
 
   // Post an event to process the attached queue.
   void PostProcessAttachedQueueEvent();
 
   // Call PostProcessAttachedQueueEvent() on a timer.
   static void PostPAQEventCallback(nsITimer* aTimer, void* aClosure);
 
+  // Enumerate each bound content's bindings (including its base bindings)
+  // in mBoundContentSet.
+  using BoundContentBindingCallback = std::function<void (nsXBLBinding*)>;
+  void EnumerateBoundContentBindings(
+    const BoundContentBindingCallback& aCallback) const;
+
 // MEMBER VARIABLES
 protected:
   // A set of nsIContent that currently have a binding installed.
   nsAutoPtr<nsTHashtable<nsRefPtrHashKey<nsIContent> > > mBoundContentSet;
 
   // A mapping from nsIContent* to nsIXPWrappedJS* (an XPConnect
   // wrapper for JS objects).  For XBL bindings that implement XPIDL
   // interfaces, and that get referred to from C++, this table caches