Revert of Internalize strings in-place

src/factory.h

 // Copyright 2014 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef V8_FACTORY_H_
 #define V8_FACTORY_H_
 
 #include "src/globals.h"
 #include "src/isolate.h"
 #include "src/messages.h"
@@ skipping 209 matching lines @@
                                               uint32_t hash_field);
 
   Handle<String> NewInternalizedStringImpl(Handle<String> string, int chars,
                                            uint32_t hash_field);
 
   // Compute the matching internalized string map for a string if possible.
   // Empty handle is returned if string is in new space or not flattened.
   MUST_USE_RESULT MaybeHandle<Map> InternalizedStringMapForString(
       Handle<String> string);
 
-  // Creates an internalized copy of an external string. |string| must be
-  // of type StringClass.
-  template <class StringClass>
-  Handle<StringClass> InternalizeExternalString(Handle<String> string);
-
   // Allocates and partially initializes an one-byte or two-byte String. The
   // characters of the string are uninitialized. Currently used in regexp code
   // only, where they are pretenured.
   MUST_USE_RESULT MaybeHandle<SeqOneByteString> NewRawOneByteString(
       int length,
       PretenureFlag pretenure = NOT_TENURED);
   MUST_USE_RESULT MaybeHandle<SeqTwoByteString> NewRawTwoByteString(
       int length,
       PretenureFlag pretenure = NOT_TENURED);
 
@@ skipping 571 matching lines @@
   void SetStrictFunctionInstanceDescriptor(Handle<Map> map,
                                            FunctionMode function_mode);
 
   void SetClassFunctionInstanceDescriptor(Handle<Map> map);
 };
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_FACTORY_H_