Split MessageKind into a MessageKind key and a MessageTemplate.

pkg/compiler/lib/src/io/start_end_information.dart

 // Copyright (c) 2015, 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.
 
 /// Source information system that maps spans of Dart AST nodes to spans of
 /// JavaScript nodes.
 
 library dart2js.source_information.start_end;
 
 import '../dart2jslib.dart' show
     MessageKind,
+    MessageTemplate,
     SourceSpan;
 import '../elements/elements.dart' show
     AstElement,
     LocalElement;
 import '../js/js.dart' as js;
 import '../js/js_source_mapping.dart';
 import '../scanner/scannerlib.dart' show Token;
 import '../tree/tree.dart' show Node, Send;
 
 import 'source_file.dart';
@@ skipping 153 matching lines @@
   SourceLocation sourceFileLocationForToken(Token token) {
     SourceLocation location =
         new OffsetSourceLocation(sourceFile, token.charOffset, name);
     checkValidSourceFileLocation(location, sourceFile, token.charOffset);
     return location;
   }
 
   void checkValidSourceFileLocation(
       SourceLocation location, SourceFile sourceFile, int offset) {
     if (!location.isValid) {
-      throw MessageKind.INVALID_SOURCE_FILE_LOCATION.message(
-          {'offset': offset,
-           'fileName': sourceFile.filename,
-           'length': sourceFile.length});
+      throw MessageTemplate.TEMPLATES[MessageKind.INVALID_SOURCE_FILE_LOCATION]
+          .message(
+              {'offset': offset,
+               'fileName': sourceFile.filename,
+               'length': sourceFile.length});
     }
   }
 
   @override
   SourceInformation buildLoop(Node node) {
     return new StartEndSourceInformation(
         sourceFileLocationForToken(node.getBeginToken()),
         sourceFileLocationForToken(node.getEndToken()));
   }
 
@@ skipping 25 matching lines @@
 
   @override
   SourceInformationBuilder forContext(
       AstElement element, {SourceInformation sourceInformation}) {
     return new StartEndSourceInformationBuilder(element);
   }
 }