Convert all symbols accessor to return read only handles so that it is not necessary to create a ne…

lib/integers.cc

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/bootstrap_natives.h"
 
 #include "vm/bigint_operations.h"
 #include "vm/dart_entry.h"
 #include "vm/exceptions.h"
 #include "vm/native_entry.h"
@@ skipping 167 matching lines @@
   if (FLAG_trace_intrinsified_natives) {
     OS::Print("Integer_equalToInteger %s == %s\n",
         left.ToCString(), right.ToCString());
   }
   return Bool::Get(left.CompareWith(right) == 0);
 }
 
 
 DEFINE_NATIVE_ENTRY(Integer_parse, 1) {
   GET_NON_NULL_NATIVE_ARGUMENT(String, value, arguments->NativeArgAt(0));
-  const String& dummy_key = String::Handle(Symbols::Empty());
-  Scanner scanner(value, dummy_key);
+  Scanner scanner(value, Symbols::Empty());
   const Scanner::GrowableTokenStream& tokens = scanner.GetStream();
   String* int_string;
   bool is_positive;
   if (Scanner::IsValidLiteral(tokens,
                              Token::kINTEGER,
                              &is_positive,
                              &int_string)) {
     if (is_positive) {
       return Integer::New(*int_string);
     }
     String& temp = String::Handle();
-    temp = String::Concat(String::Handle(Symbols::New("-")), *int_string);
+    temp = String::Concat(Symbols::Dash(), *int_string);
     return Integer::New(temp);
   }
 
   const Array& args = Array::Handle(Array::New(1));
   args.SetAt(0, value);
   Exceptions::ThrowByType(Exceptions::kFormat, args);
   return Object::null();
 }
 
 
@@ skipping 96 matching lines @@
 
 DEFINE_NATIVE_ENTRY(Bigint_bitNegate, 1) {
   const Bigint& value = Bigint::CheckedHandle(arguments->NativeArgAt(0));
   const Bigint& result = Bigint::Handle(BigintOperations::BitNot(value));
   ASSERT(CheckInteger(value));
   ASSERT(CheckInteger(result));
   return result.AsValidInteger();
 }
 
 }  // namespace dart