[builtins] Unify the String constructor.

src/runtime/runtime-symbol.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/arguments.h"
+#include "src/isolate-inl.h"
 #include "src/objects-inl.h"
+#include "src/string-builder.h"
 
 namespace v8 {
 namespace internal {
 
 RUNTIME_FUNCTION(Runtime_CreateSymbol) {
   HandleScope scope(isolate);
   DCHECK(args.length() == 1);
   CONVERT_ARG_HANDLE_CHECKED(Object, name, 0);
   RUNTIME_ASSERT(name->IsString() || name->IsUndefined());
   Handle<Symbol> symbol = isolate->factory()->NewSymbol();
@@ skipping 12 matching lines @@
 
 
 RUNTIME_FUNCTION(Runtime_SymbolDescription) {
   SealHandleScope shs(isolate);
   DCHECK(args.length() == 1);
   CONVERT_ARG_CHECKED(Symbol, symbol, 0);
   return symbol->name();
 }
 
 
+RUNTIME_FUNCTION(Runtime_SymbolDescriptiveString) {
+  HandleScope scope(isolate);
+  DCHECK_EQ(1, args.length());
+  CONVERT_ARG_HANDLE_CHECKED(Symbol, symbol, 0);
+  IncrementalStringBuilder builder(isolate);
+  builder.AppendCString("Symbol(");
+  if (symbol->name()->IsString()) {
+    builder.AppendString(handle(String::cast(symbol->name()), isolate));
+  }
+  builder.AppendCharacter(')');
+  Handle<String> result;
+  ASSIGN_RETURN_FAILURE_ON_EXCEPTION(isolate, result, builder.Finish());
+  return *result;
+}
+
+
 RUNTIME_FUNCTION(Runtime_SymbolRegistry) {
   HandleScope scope(isolate);
   DCHECK(args.length() == 0);
   return *isolate->GetSymbolRegistry();
 }
 
 
 RUNTIME_FUNCTION(Runtime_SymbolIsPrivate) {
   SealHandleScope shs(isolate);
   DCHECK(args.length() == 1);
   CONVERT_ARG_CHECKED(Symbol, symbol, 0);
   return isolate->heap()->ToBoolean(symbol->is_private());
 }
 }  // namespace internal
 }  // namespace v8