--- a/intl/strres/nsIStringBundle.idl
+++ b/intl/strres/nsIStringBundle.idl
@@ -78,17 +78,16 @@ interface nsIStringBundle : nsISupports
   virtual size_t SizeOfIncludingThisIfUnshared(mozilla::MallocSizeOf aMallocSizeOf) const = 0;
 %}
 };
 
 [scriptable, uuid(D85A17C0-AA7C-11d2-9B8C-00805F8A16D9)]
 interface nsIStringBundleService : nsISupports
 {
   nsIStringBundle createBundle(in string aURLSpec);
-  nsIStringBundle createExtensibleBundle(in string aRegistryKey);
 
   /**
    * Formats a message string from a status code and status arguments.
    * @param aStatus - The status code. This is mapped into a string ID and
    *            and used in the string lookup process (see nsIErrorService).
    * @param aStatusArg - The status message argument(s). Multiple arguments
    *            can be separated by newline ('\n') characters.
    * @return the formatted message

--- a/intl/strres/nsStringBundle.cpp
+++ b/intl/strres/nsStringBundle.cpp
@@ -611,185 +611,16 @@ nsStringBundleBase::FormatString(const c
                             aLength >= 7 ? aParams[6] : nullptr,
                             aLength >= 8 ? aParams[7] : nullptr,
                             aLength >= 9 ? aParams[8] : nullptr,
                             aLength >= 10 ? aParams[9] : nullptr);
 
   return NS_OK;
 }
 
-NS_IMPL_ISUPPORTS(nsExtensibleStringBundle, nsIStringBundle)
-
-nsExtensibleStringBundle::nsExtensibleStringBundle()
-{
-  mLoaded = false;
-}
-
-nsresult
-nsExtensibleStringBundle::Init(const char * aCategory,
-                               nsIStringBundleService* aBundleService)
-{
-
-  nsresult rv;
-  nsCOMPtr<nsICategoryManager> catman =
-    do_GetService(NS_CATEGORYMANAGER_CONTRACTID, &rv);
-  if (NS_FAILED(rv)) return rv;
-
-  nsCOMPtr<nsISimpleEnumerator> enumerator;
-  rv = catman->EnumerateCategory(aCategory, getter_AddRefs(enumerator));
-  if (NS_FAILED(rv)) return rv;
-
-  bool hasMore;
-  while (NS_SUCCEEDED(enumerator->HasMoreElements(&hasMore)) && hasMore) {
-    nsCOMPtr<nsISupports> supports;
-    rv = enumerator->GetNext(getter_AddRefs(supports));
-    if (NS_FAILED(rv))
-      continue;
-
-    nsCOMPtr<nsISupportsCString> supStr = do_QueryInterface(supports, &rv);
-    if (NS_FAILED(rv))
-      continue;
-
-    nsAutoCString name;
-    rv = supStr->GetData(name);
-    if (NS_FAILED(rv))
-      continue;
-
-    nsCOMPtr<nsIStringBundle> bundle;
-    rv = aBundleService->CreateBundle(name.get(), getter_AddRefs(bundle));
-    if (NS_FAILED(rv))
-      continue;
-
-    mBundles.AppendObject(bundle);
-  }
-
-  return rv;
-}
-
-NS_IMETHODIMP
-nsExtensibleStringBundle::AsyncPreload()
-{
-  nsresult rv = NS_OK;
-  const uint32_t size = mBundles.Count();
-  for (uint32_t i = 0; i < size; ++i) {
-    nsIStringBundle* bundle = mBundles[i];
-    if (bundle) {
-      nsresult rv2 = bundle->AsyncPreload();
-      rv = NS_FAILED(rv) ? rv : rv2;
-    }
-  }
-  return rv;
-}
-
-nsExtensibleStringBundle::~nsExtensibleStringBundle()
-{
-}
-
-size_t
-nsExtensibleStringBundle::SizeOfIncludingThis(mozilla::MallocSizeOf aMallocSizeOf) const
-{
-  size_t n = 0;
-  const uint32_t sz = mBundles.Count();
-  for (uint32_t i = 0; i < sz; ++i) {
-    nsIStringBundle* bundle = mBundles[i];
-    if (bundle) {
-      n += bundle->SizeOfIncludingThis(aMallocSizeOf);
-    }
-  }
-  n += mBundles.ShallowSizeOfExcludingThis(aMallocSizeOf);
-  return aMallocSizeOf(this) + n;
-}
-
-size_t
-nsExtensibleStringBundle::SizeOfIncludingThisIfUnshared(MallocSizeOf aMallocSizeOf) const
-{
-  if (mRefCnt == 1) {
-    return SizeOfIncludingThis(aMallocSizeOf);
-  } else {
-    return 0;
-  }
-}
-
-nsresult
-nsExtensibleStringBundle::GetStringFromID(int32_t aID, nsAString& aResult)
-{
-  nsAutoCString idStr;
-  idStr.AppendInt(aID, 10);
-  return GetStringFromName(idStr.get(), aResult);
-}
-
-nsresult
-nsExtensibleStringBundle::GetStringFromAUTF8Name(const nsACString& aName,
-                                                 nsAString& aResult)
-{
-  return GetStringFromName(PromiseFlatCString(aName).get(), aResult);
-}
-
-nsresult
-nsExtensibleStringBundle::GetStringFromName(const char* aName,
-                                            nsAString& aResult)
-{
-  nsresult rv;
-  const uint32_t size = mBundles.Count();
-  for (uint32_t i = 0; i < size; ++i) {
-    nsIStringBundle* bundle = mBundles[i];
-    if (bundle) {
-      rv = bundle->GetStringFromName(aName, aResult);
-      if (NS_SUCCEEDED(rv))
-        return NS_OK;
-    }
-  }
-
-  return NS_ERROR_FAILURE;
-}
-
-NS_IMETHODIMP
-nsExtensibleStringBundle::FormatStringFromID(int32_t aID,
-                                             const char16_t ** aParams,
-                                             uint32_t aLength,
-                                             nsAString& aResult)
-{
-  nsAutoCString idStr;
-  idStr.AppendInt(aID, 10);
-  return FormatStringFromName(idStr.get(), aParams, aLength, aResult);
-}
-
-NS_IMETHODIMP
-nsExtensibleStringBundle::FormatStringFromAUTF8Name(const nsACString& aName,
-                                                    const char16_t ** aParams,
-                                                    uint32_t aLength,
-                                                    nsAString& aResult)
-{
-  return FormatStringFromName(PromiseFlatCString(aName).get(),
-                              aParams, aLength, aResult);
-}
-
-NS_IMETHODIMP
-nsExtensibleStringBundle::FormatStringFromName(const char* aName,
-                                               const char16_t** aParams,
-                                               uint32_t aLength,
-                                               nsAString& aResult)
-{
-  nsAutoString formatStr;
-  nsresult rv;
-  rv = GetStringFromName(aName, formatStr);
-  if (NS_FAILED(rv))
-    return rv;
-
-  return nsStringBundle::FormatString(formatStr.get(), aParams, aLength,
-                                      aResult);
-}
-
-nsresult nsExtensibleStringBundle::GetSimpleEnumeration(nsISimpleEnumerator ** aResult)
-{
-  // XXX write me
-  *aResult = nullptr;
-  return NS_ERROR_NOT_IMPLEMENTED;
-}
-
 /////////////////////////////////////////////////////////////////////////////////////////
 
 #define MAX_CACHED_BUNDLES 16
 
 struct bundleCacheEntry_t final : public LinkedListElement<bundleCacheEntry_t> {
   nsCString mHashKey;
   nsCOMPtr<nsIStringBundle> mBundle;
 
@@ -1034,34 +865,16 @@ nsStringBundleService::insertIntoCache(a
 NS_IMETHODIMP
 nsStringBundleService::CreateBundle(const char* aURLSpec,
                                     nsIStringBundle** aResult)
 {
   getStringBundle(aURLSpec,aResult);
   return NS_OK;
 }
 
-NS_IMETHODIMP
-nsStringBundleService::CreateExtensibleBundle(const char* aCategory,
-                                              nsIStringBundle** aResult)
-{
-  NS_ENSURE_ARG_POINTER(aResult);
-  *aResult = nullptr;
-
-  RefPtr<nsExtensibleStringBundle> bundle = new nsExtensibleStringBundle();
-
-  nsresult res = bundle->Init(aCategory, this);
-  if (NS_FAILED(res)) {
-    return res;
-  }
-
-  bundle.forget(aResult);
-  return NS_OK;
-}
-
 #define GLOBAL_PROPERTIES "chrome://global/locale/global-strres.properties"
 
 nsresult
 nsStringBundleService::FormatWithBundle(nsIStringBundle* bundle, nsresult aStatus,
                                         uint32_t argCount, char16_t** argArray,
                                         nsAString& result)
 {
   nsresult rv;

--- a/intl/strres/nsStringBundle.h
+++ b/intl/strres/nsStringBundle.h
@@ -64,38 +64,9 @@ public:
 protected:
     virtual ~nsStringBundle();
 
     nsresult GetStringImpl(const nsACString& aName, nsAString& aResult) override;
 
     nsresult GetSimpleEnumerationImpl(nsISimpleEnumerator** elements) override;
 };
 
-class nsExtensibleStringBundle;
-
-/**
- * An extensible implementation of the StringBundle interface.
- *
- * @created         28/Dec/1999
- * @author  Catalin Rotaru [CATA]
- */
-class nsExtensibleStringBundle final : public nsIStringBundle
-{
-  NS_DECL_ISUPPORTS
-  NS_DECL_NSISTRINGBUNDLE
-
-  nsresult Init(const char * aCategory, nsIStringBundleService *);
-
-public:
-  nsExtensibleStringBundle();
-  size_t SizeOfIncludingThis(mozilla::MallocSizeOf aMallocSizeOf) const override;
-  size_t SizeOfIncludingThisIfUnshared(mozilla::MallocSizeOf aMallocSizeOf) const override;
-
-private:
-  virtual ~nsExtensibleStringBundle();
-
-  nsCOMArray<nsIStringBundle> mBundles;
-  bool mLoaded;
-};
-
-
-
 #endif