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

lib/double.cc

Index: lib/double.cc
===================================================================
--- lib/double.cc	(revision 16583)
+++ lib/double.cc	(working copy)
@@ -206,8 +206,7 @@
 
 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;