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

vm/scanner.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/scanner.h"
 
 #include "platform/assert.h"
 #include "vm/flags.h"
 #include "vm/object.h"
 #include "vm/object_store.h"
@@ skipping 408 matching lines @@
     // The script tag extends to the end of the line. Just treat this
     // similar to a line comment.
     SkipLine();
     return;
   }
   if (!IsLetter(c0_)) {
     ErrorMsg("Unrecognized library tag");
     SkipLine();
     return;
   }
-  const String& kLibrary = String::Handle(Symbols::Library());
-  const String& kImport = String::Handle(Symbols::Import());
-  const String& kSource = String::Handle(Symbols::Source());
   const String& ident = String::Handle(ConsumeIdentChars(false));
-  if (ident.Equals(kLibrary)) {
+  if (ident.Equals(Symbols::Library())) {
     current_token_.kind = Token::kLEGACY_LIBRARY;
     return;
   }
-  if (ident.Equals(kImport)) {
+  if (ident.Equals(Symbols::Import())) {
     current_token_.kind = Token::kLEGACY_IMPORT;
     return;
   }
-  if (ident.Equals(kSource)) {
+  if (ident.Equals(Symbols::Source())) {
     current_token_.kind = Token::kLEGACY_SOURCE;
     return;
   }
   ErrorMsg("Unrecognized library token");
   SkipLine();
 }
 
 
 void Scanner::ScanLiteralString(bool is_raw) {
   ASSERT(!IsScanningString());
@@ skipping 534 matching lines @@
               "%c%#"Px"", kPrivateKeySeparator, key_value);
   const String& result = String::Handle(String::New(private_key, Heap::kOld));
   return result.raw();
 }
 
 
 void Scanner::InitOnce() {
 }
 
 }  // namespace dart