Add support for analyzing individual URIs.

tests/compiler/dart2js/js_backend_cps_ir_source_information_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.
 
 // Test that the CPS IR code generator generates source information.
 
 library source_information_tests;
 
 import 'package:async_helper/async_helper.dart';
 import 'package:expect/expect.dart';
@@ skipping 48 matching lines @@
   }
 
   js.Node ast = compiler.enqueuer.codegen.generatedCode[foundElement];
   return js.prettyPrint(ast, compiler).getText();
 }
 
 runTests(List<TestEntry> tests) {
   for (TestEntry test in tests) {
     Map files = {TEST_MAIN_FILE: test.source};
     asyncTest(() {
-      Compiler compiler = compilerFor(files, options: <String>['--use-cps-ir']);
+      Compiler compiler = compilerFor(
+          memorySourceFiles: files, options: <String>['--use-cps-ir']);
       ir.FunctionDefinition irNodeForMain;
 
       void cacheIrNodeForMain(Element function, ir.FunctionDefinition irNode) {
         if (function == compiler.mainFunction) {
           assert(irNodeForMain == null);
           irNodeForMain = irNode;
         }
       }
 
       Uri uri = Uri.parse('memory:$TEST_MAIN_FILE');
@@ skipping 59 matching lines @@
   print('Hello');
   print('World');
 }
 """, const ['memory:test.dart:[2,3]',
             'memory:test.dart:[3,3]']),
 ];
 
 void main() {
   runTests(tests);
 }