[es6] Implement spec compliant ToPrimitive in the runtime.

src/runtime/runtime-scopes.cc

 // 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.
 
 #include "src/runtime/runtime-utils.h"
 
 #include "src/accessors.h"
 #include "src/arguments.h"
 #include "src/frames-inl.h"
 #include "src/messages.h"
@@ skipping 1121 matching lines @@
     ASSIGN_RETURN_FAILURE_ON_EXCEPTION(
         isolate, result,
         Object::GetProperty(isolate->initial_object_prototype(),
                             Handle<Symbol>::cast(raw_key)));
     return *result;
   }
 
   // Convert the key to a string.
   Handle<Object> converted;
   ASSIGN_RETURN_FAILURE_ON_EXCEPTION(isolate, converted,
-                                     Execution::ToString(isolate, raw_key));
+                                     Object::ToString(isolate, raw_key));
   Handle<String> key = Handle<String>::cast(converted);
 
   // Try to convert the string key into an array index.
   if (key->AsArrayIndex(&index)) {
     if (index < n) {
       return frame->GetParameter(index);
     } else {
       Handle<Object> initial_prototype(isolate->initial_object_prototype());
       Handle<Object> result;
       ASSIGN_RETURN_FAILURE_ON_EXCEPTION(
@@ skipping 18 matching lines @@
 
   // Lookup in the initial Object.prototype object.
   Handle<Object> result;
   ASSIGN_RETURN_FAILURE_ON_EXCEPTION(
       isolate, result,
       Object::GetProperty(isolate->initial_object_prototype(), key));
   return *result;
 }
 }  // namespace internal
 }  // namespace v8