diff --git a/dom/base/DirectionalityUtils.cpp b/dom/base/DirectionalityUtils.cpp
index 753ddbaf31e7..09f4b199fdfa 100644
--- a/dom/base/DirectionalityUtils.cpp
+++ b/dom/base/DirectionalityUtils.cpp
@@ -490,15 +490,15 @@ private:
     return map;
   }
 
-  static PLDHashOperator SetNodeDirection(nsPtrHashKey<Element>* aEntry, void* aDir)
+  static nsCheapSetOperator SetNodeDirection(nsPtrHashKey<Element>* aEntry, void* aDir)
   {
     MOZ_ASSERT(aEntry->GetKey()->IsElement(), "Must be an Element");
     aEntry->GetKey()->SetDirectionality(*reinterpret_cast<Directionality*>(aDir),
                                         true);
-    return PL_DHASH_NEXT;
+    return OpNext;
   }
 
-  static PLDHashOperator ResetNodeDirection(nsPtrHashKey<Element>* aEntry, void* aData)
+  static nsCheapSetOperator ResetNodeDirection(nsPtrHashKey<Element>* aEntry, void* aData)
   {
     MOZ_ASSERT(aEntry->GetKey()->IsElement(), "Must be an Element");
     // run the downward propagation algorithm
@@ -516,15 +516,15 @@ private:
       rootNode->ClearHasDirAutoSet();
       rootNode->UnsetProperty(nsGkAtoms::dirAutoSetBy);
     }
-    return PL_DHASH_REMOVE;
+    return OpRemove;
   }
 
-  static PLDHashOperator ClearEntry(nsPtrHashKey<Element>* aEntry, void* aData)
+  static nsCheapSetOperator ClearEntry(nsPtrHashKey<Element>* aEntry, void* aData)
   {
     Element* rootNode = aEntry->GetKey();
     rootNode->ClearHasDirAutoSet();
     rootNode->UnsetProperty(nsGkAtoms::dirAutoSetBy);
-    return PL_DHASH_REMOVE;
+    return OpRemove;
   }
 
 public:
diff --git a/xpcom/ds/nsCheapSets.h b/xpcom/ds/nsCheapSets.h
index 2ebcc012ab67..e61febffe5a6 100644
--- a/xpcom/ds/nsCheapSets.h
+++ b/xpcom/ds/nsCheapSets.h
@@ -10,6 +10,12 @@
 #include "nsTHashtable.h"
 #include <stdint.h>
 
+enum nsCheapSetOperator
+{
+  OpNext = 0,   // enumerator says continue
+  OpRemove = 1, // enumerator says remove and continue
+};
+
 /**
  * A set that takes up minimal size when there are 0 or 1 entries in the set.
  * Use for cases where sizes of 0 and 1 are even slightly common.
@@ -19,7 +25,7 @@ class nsCheapSet
 {
 public:
   typedef typename EntryType::KeyType KeyType;
-  typedef PLDHashOperator (*Enumerator)(EntryType* aEntry, void* userArg);
+  typedef nsCheapSetOperator (*Enumerator)(EntryType* aEntry, void* userArg);
 
   nsCheapSet() : mState(ZERO) {}
   ~nsCheapSet() { Clear(); }
@@ -70,13 +76,21 @@ public:
       case ZERO:
         return 0;
       case ONE:
-        if (aEnumFunc(GetSingleEntry(), aUserArg) == PL_DHASH_REMOVE) {
+        if (aEnumFunc(GetSingleEntry(), aUserArg) == OpRemove) {
           GetSingleEntry()->~EntryType();
           mState = ZERO;
         }
         return 1;
-      case MANY:
-        return mUnion.table->EnumerateEntries(aEnumFunc, aUserArg);
+      case MANY: {
+        uint32_t n = mUnion.table->Count();
+        for (auto iter = mUnion.table->Iter(); !iter.Done(); iter.Next()) {
+          auto entry = static_cast<EntryType*>(iter.Get());
+          if (aEnumFunc(entry, aUserArg) == OpRemove) {
+            iter.Remove();
+          }
+        }
+        return n;
+      }
       default:
         NS_NOTREACHED("bogus state");
         return 0;