Remove deprecated StringBuffer.add, addAll and addCharCode.

utils/template/tool.dart

 // 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.
 
 library templatetool;
 
 import 'dart:io';
 import 'template.dart';
 import '../lib/file_system.dart';
 import '../lib/file_system_vm.dart';
@@ skipping 75 matching lines @@
     final parsedElapsed = time(() {
       templates = templateParseAndValidate(source);
     });
 
     StringBuffer code = new StringBuffer();
 
     num codegenElapsed;
     if (world.errors == 0) {
       // Generate the Dart class(es) for all template(s).
       codegenElapsed = time(() {
-        code.add(Codegen.generate(templates, outFilename));
+        code.write(Codegen.generate(templates, outFilename));
       });
     }
 
     printStats("Parsed", parsedElapsed, sourceFullFn);
     printStats("Codegen", codegenElapsed, sourceFullFn);
 
     final outputElapsed = time(() {
       files.writeString(outputFullFn, code.toString());
     });
 
     printStats("Wrote file", codegenElapsed, outputFullFn);
   }
 }