Split MessageKind into a MessageKind key and a MessageTemplate.

tests/compiler/dart2js/compiler_test.dart

 // 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.
 
 import "dart:async";
 import "package:expect/expect.dart";
 import "package:async_helper/async_helper.dart";
 import "package:compiler/src/dart2jslib.dart";
 import "package:compiler/src/elements/elements.dart";
 import "package:compiler/src/resolution/resolution.dart";
 import "package:compiler/src/util/util.dart";
 import "mock_compiler.dart";
 
 
 class CallbackMockCompiler extends MockCompiler {
   CallbackMockCompiler() : super.internal();
 
   var onError;
   var onWarning;
 
   setOnError(var f) => onError = f;
   setOnWarning(var f) => onWarning = f;
 
   void reportWarning(Spannable node,
                      MessageKind messageKind,
                      [Map arguments = const {}]) {
     if (onWarning != null) {
-      onWarning(this, node, messageKind.message(arguments));
+      MessageTemplate template = MessageTemplate.TEMPLATES[messageKind];
+      onWarning(this, node, template.message(arguments));
     }
     super.reportWarning(node, messageKind, arguments);
   }
 
   void reportError(Spannable node,
                    MessageKind messageKind,
                    [Map arguments = const {}]) {
     if (onError != null) {
-      onError(this, node, messageKind.message(arguments));
+      MessageTemplate template = MessageTemplate.TEMPLATES[messageKind];
+      onError(this, node, template.message(arguments));
     }
     super.reportError(node, messageKind, arguments);
   }
 }
 
 Future testErrorHandling() {
   // Test that compiler.currentElement is set correctly when
   // reporting errors/warnings.
   CallbackMockCompiler compiler = new CallbackMockCompiler();
   return compiler.init().then((_) {
     ResolverVisitor visitor = compiler.resolverVisitor();
     compiler.parseScript('NoSuchPrefix.NoSuchType foo() {}');
     FunctionElement foo = compiler.mainApp.find('foo');
     compiler.setOnWarning(
         (c, n, m) => Expect.equals(foo, compiler.currentElement));
     foo.computeType(compiler);
     Expect.equals(1, compiler.warnings.length);
   });
 }
 
 main() {
   asyncTest(() => testErrorHandling());
 }