Add support for analyzing individual URIs.

tests/compiler/dart2js/message_kind_helper.dart

 // Copyright (c) 2013, 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 dart2js.test.message_kind_helper;
 
 import 'package:expect/expect.dart';
 import 'dart:async';
 
 import 'package:compiler/src/compiler.dart' show
@@ skipping 64 matching lines @@
       messages.add(message);
     }
 
     bool oldBackendIsDart;
     if (cachedCompiler != null) {
       oldBackendIsDart = cachedCompiler.backend is DartBackend;
     }
     bool newBackendIsDart = template.options.contains('--output-type=dart');
 
     Compiler compiler = compilerFor(
-        example,
+        memorySourceFiles: example,
         diagnosticHandler: new LegacyCompilerDiagnostics(collect),
         options: ['--analyze-only',
                   '--enable-experimental-mirrors']..addAll(template.options),
         cachedCompiler:
              // TODO(johnniwinther): Remove this restriction when constant
              // values can be computed directly from the expressions.
              oldBackendIsDart == newBackendIsDart ? cachedCompiler : null);
 
     return compiler.run(Uri.parse('memory:main.dart')).then((_) {
 
@@ skipping 46 matching lines @@
                     kindsWithPendingClasses.contains(template));
 
       if (!pendingStuff) {
         // If there is pending stuff, or the compiler was cancelled, we
         // shouldn't reuse the compiler.
         cachedCompiler = compiler;
       }
     });
   }).then((_) => cachedCompiler);
 }