Add support for analyzing individual URIs.

tests/compiler/dart2js/serialization_analysis_test.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.
 
 library dart2js.serialization_analysis_test;
 
 import 'dart:async';
 import 'package:async_helper/async_helper.dart';
 import 'package:expect/expect.dart';
 import 'package:compiler/src/elements/elements.dart';
@@ skipping 183 matching lines @@
         diagnosticCollector.warnings.length,
         "Unexpected warning count.");
     Expect.equals(test.expectedHintCount, diagnosticCollector.hints.length,
         "Unexpected hint count.");
     Expect.equals(test.expectedInfoCount, diagnosticCollector.infos.length,
         "Unexpected info count.");
   }
 }
 
 Future<String> serializeDartCore() async {
-  Compiler compiler = compilerFor({},
+  Compiler compiler = compilerFor(
       options: ['--analyze-all', '--output-type=dart']);
   await compiler.runCompiler(Uri.parse('dart:core'));
   return serialize(compiler.libraryLoader.libraries);
 }
 
 String serialize(Iterable<LibraryElement> libraries) {
   Serializer serializer = new Serializer(const JsonSerializationEncoder());
   for (LibraryElement library in libraries) {
     serializer.serialize(library);
   }
@@ skipping 17 matching lines @@
   @override
   WorldImpact computeWorldImpact(Element element) {
     return const WorldImpact();
   }
 
   @override
   bool isDeserialized(Element element) {
     return deserializedLibraries.contains(element.library);
   }
 }