[es2015] Precompute the descriptive string for symbols.

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/feedback-vector.h"
 #include "src/globals.h"
 #include "src/isolate.h"
@@ skipping 249 matching lines @@
       const ExternalOneByteString::Resource* resource);
   MUST_USE_RESULT MaybeHandle<String> NewExternalStringFromTwoByte(
       const ExternalTwoByteString::Resource* resource);
   // Create a new external string object for one-byte encoded native script.
   // It does not cache the resource data pointer.
   Handle<ExternalOneByteString> NewNativeSourceString(
       const ExternalOneByteString::Resource* resource);
 
   // Create a symbol.
   Handle<Symbol> NewSymbol();
+  MaybeHandle<Symbol> NewSymbol(Handle<Object> name);
   Handle<Symbol> NewPrivateSymbol();
+  MaybeHandle<Symbol> NewPrivateSymbol(Handle<Object> name);
 
   // Create a promise.
   Handle<JSPromise> NewJSPromise();
 
   // Create a global (but otherwise uninitialized) context.
   Handle<Context> NewNativeContext();
 
   // Create a script context.
   Handle<Context> NewScriptContext(Handle<JSFunction> function,
                                    Handle<ScopeInfo> scope_info);
@@ skipping 562 matching lines @@
   void SetStrictFunctionInstanceDescriptor(Handle<Map> map,
                                            FunctionMode function_mode);
 
   void SetClassFunctionInstanceDescriptor(Handle<Map> map);
 };
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_FACTORY_H_