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

lib/double.cc

 // Copyright (c) 2011, 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 <math.h>
 
 #include "vm/bootstrap_natives.h"
 
 #include "vm/bigint_operations.h"
 #include "vm/double_conversion.h"
@@ skipping 188 matching lines @@
   } else if ((Mint::kMinValue <= result) && (result <= Mint::kMaxValue)) {
     return Mint::New(static_cast<int64_t>(result));
   } else {
     return BigintOperations::NewFromDouble(result);
   }
 }
 
 
 DEFINE_NATIVE_ENTRY(Double_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* number_string;
   bool is_positive;
   if (Scanner::IsValidLiteral(tokens,
                               Token::kDOUBLE,
                               &is_positive,
                               &number_string)) {
     const char* cstr = number_string->ToCString();
     char* p_end = NULL;
     double double_value = strtod(cstr, &p_end);
@@ skipping 109 matching lines @@
 
 DEFINE_NATIVE_ENTRY(Double_getIsNegative, 1) {
   const Double& arg = Double::CheckedHandle(arguments->NativeArgAt(0));
   // Include negative zero, infinity.
   return Bool::Get(signbit(arg.value()) && !isnan(arg.value()));
 }
 
 // Add here only functions using/referring to old-style casts.
 
 }  // namespace dart