--- a/dom/base/nsScriptNameSpaceManager.cpp
+++ b/dom/base/nsScriptNameSpaceManager.cpp
@@ -197,41 +197,16 @@ nsScriptNameSpaceManager::LookupName(con
 
   if (aClassName) {
     *aClassName = nullptr;
   }
   return nullptr;
 }
 
 nsresult
-nsScriptNameSpaceManager::RegisterClassName(const char *aClassName,
-                                            int32_t aDOMClassInfoID,
-                                            const char16_t **aResult)
-{
-  if (!nsCRT::IsAscii(aClassName)) {
-    NS_ERROR("Trying to register a non-ASCII class name");
-    return NS_OK;
-  }
-  nsGlobalNameStruct *s = AddToHash(aClassName, aResult);
-  NS_ENSURE_TRUE(s, NS_ERROR_OUT_OF_MEMORY);
-
-  if (s->mType == nsGlobalNameStruct::eTypeClassConstructor) {
-    return NS_OK;
-  }
-
-  NS_ASSERTION(s->mType == nsGlobalNameStruct::eTypeNotInitialized,
-               "Whaaa, JS environment name clash!");
-
-  s->mType = nsGlobalNameStruct::eTypeClassConstructor;
-  s->mDOMClassInfoID = aDOMClassInfoID;
-
-  return NS_OK;
-}
-
-nsresult
 nsScriptNameSpaceManager::OperateCategoryEntryHash(nsICategoryManager* aCategoryManager,
                                                    const char* aCategory,
                                                    nsISupports* aEntry,
                                                    bool aRemove)
 {
   MOZ_ASSERT(aCategoryManager);
   // Get the type from the category name.
   // NOTE: we could have passed the type in FillHash() and guessed it in

--- a/dom/base/nsScriptNameSpaceManager.h
+++ b/dom/base/nsScriptNameSpaceManager.h
@@ -66,20 +66,16 @@ public:
   // Returns a nsGlobalNameStruct for aName, or null if one is not
   // found. The returned nsGlobalNameStruct is only guaranteed to be
   // valid until the next call to any of the methods in this class.
   // It also returns a pointer to the string buffer of the classname
   // in the nsGlobalNameStruct.
   const nsGlobalNameStruct* LookupName(const nsAString& aName,
                                        const char16_t **aClassName = nullptr);
 
-  nsresult RegisterClassName(const char *aClassName,
-                             int32_t aDOMClassInfoID,
-                             const char16_t **aResult);
-
   class NameIterator : public PLDHashTable::Iterator
   {
   public:
     typedef PLDHashTable::Iterator Base;
     explicit NameIterator(PLDHashTable* aTable) : Base(aTable) {}
     NameIterator(NameIterator&& aOther) : Base(mozilla::Move(aOther.mTable)) {}
 
     const GlobalNameMapEntry* Get() const