Revert "Handlify concat string and substring."

src/handles.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 211 matching lines @@
 
 
 Handle<Object> GetProperty(Isolate* isolate,
                            Handle<Object> obj,
                            Handle<Object> key) {
   CALL_HEAP_FUNCTION(isolate,
                      Runtime::GetObjectProperty(isolate, obj, key), Object);
 }
 
 
-Handle<String> LookupSingleCharacterStringFromCode(Isolate* isolate,
+Handle<Object> LookupSingleCharacterStringFromCode(Isolate* isolate,
                                                    uint32_t index) {
   CALL_HEAP_FUNCTION(
       isolate,
-      isolate->heap()->LookupSingleCharacterStringFromCode(index),
-      String);
+      isolate->heap()->LookupSingleCharacterStringFromCode(index), Object);
 }
 
 
 // Wrappers for scripts are kept alive and cached in weak global
 // handles referred from foreign objects held by the scripts as long as
 // they are used. When they are not used anymore, the garbage
 // collector will call the weak callback on the global handle
 // associated with the wrapper and get rid of both the wrapper and the
 // handle.
 static void ClearWrapperCache(v8::Isolate* v8_isolate,
@@ skipping 566 matching lines @@
                                    Handle<Code> code) {
   heap->EnsureWeakObjectToCodeTable();
   Handle<DependentCode> dep(heap->LookupWeakObjectToCodeDependency(*object));
   dep = DependentCode::Insert(dep, DependentCode::kWeaklyEmbeddedGroup, code);
   CALL_HEAP_FUNCTION_VOID(heap->isolate(),
                           heap->AddWeakObjectToCodeDependency(*object, *dep));
 }
 
 
 } }  // namespace v8::internal