[es2015] Precompute the descriptive string for symbols.

src/isolate.cc

 // Copyright 2012 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/isolate.h"
 
 #include <stdlib.h>
 
 #include <fstream>  // NOLINT(readability/streams)
 #include <sstream>
@@ skipping 3252 matching lines @@
 #endif
 
 Handle<Symbol> Isolate::SymbolFor(Heap::RootListIndex dictionary_index,
                                   Handle<String> name, bool private_symbol) {
   Handle<String> key = factory()->InternalizeString(name);
   Handle<NameDictionary> dictionary =
       Handle<NameDictionary>::cast(heap()->root_handle(dictionary_index));
   int entry = dictionary->FindEntry(key);
   Handle<Symbol> symbol;
   if (entry == NameDictionary::kNotFound) {
-    symbol =
-        private_symbol ? factory()->NewPrivateSymbol() : factory()->NewSymbol();
-    symbol->set_name(*key);
+    symbol = private_symbol ? factory()->NewPrivateSymbol(key).ToHandleChecked()
+                            : factory()->NewSymbol(key).ToHandleChecked();
     dictionary = NameDictionary::Add(dictionary, key, symbol,
                                      PropertyDetails::Empty(), &entry);
     switch (dictionary_index) {
       case Heap::kPublicSymbolTableRootIndex:
         symbol->set_is_public(true);
         heap()->set_public_symbol_table(*dictionary);
         break;
       case Heap::kApiSymbolTableRootIndex:
         heap()->set_api_symbol_table(*dictionary);
         break;
@@ skipping 490 matching lines @@
   // Then check whether this scope intercepts.
   if ((flag & intercept_mask_)) {
     intercepted_flags_ |= flag;
     return true;
   }
   return false;
 }
 
 }  // namespace internal
 }  // namespace v8