Added 'dynamic' keyword, so that 'Dynamic' can be deprecated.

tests/compiler/dart2js/compiler_helper.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.
 // Test constant folding.
 
 #library("compiler_helper");
 
 #import("dart:uri");
 
 #import("../../../lib/compiler/implementation/elements/elements.dart", prefix: "lego");
@@ skipping 29 matching lines @@
 
 String compileAll(String code) {
   Uri uri = new Uri.fromComponents(scheme: 'source');
   MockCompiler compiler = compilerFor(code, uri);
   compiler.runCompiler(uri);
   Expect.isFalse(compiler.compilationFailed,
                  'Unexpected compilation error');
   return compiler.assembledCode;
 }
 
-Dynamic compileAndCheck(String code,
+dynamic compileAndCheck(String code,
                         String name,
                         check(MockCompiler compiler, lego.Element element)) {
   Uri uri = new Uri.fromComponents(scheme: 'source');
   MockCompiler compiler = compilerFor(code, uri);
   compiler.runCompiler(uri);
   lego.Element element = findElement(compiler, name);
   return check(compiler, element);
 }
 
 lego.Element findElement(compiler, String name) {
@@ skipping 26 matching lines @@
                 '"$generated" does not match /$regexp/');
 }
 
 void compileAndDoNotMatch(String code, String entry, RegExp regexp) {
   String generated = compile(code, entry);
   Expect.isFalse(regexp.hasMatch(generated),
                  '"$generated" has a match in /$regexp/');
 }
 
 int length(Link link) => link.isEmpty() ? 0 : length(link.tail) + 1;