Fix hidden try tests.

tests/try/poi/poi_find_test.dart

 // Copyright (c) 2014, 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 poi.dart finds the right element.
 
 library trydart.poi_find_test;
 
 import 'dart:io' show
     Platform;
@@ skipping 17 matching lines @@
   Uri script = Platform.script.resolve('data/empty_main.dart');
   FormattingDiagnosticHandler handler = new FormattingDiagnosticHandler();
   handler.verbose = false;
 
   Future future = poi.runPoi(script, 225, handler.provider, handler);
   return future.then((Element element) {
     Uri foundScript = element.compilationUnit.script.resourceUri;
     Expect.stringEquals('$script', '$foundScript');
     Expect.stringEquals('main', element.name);
 
-    String source = handler.provider.sourceFiles['$script'].slowText();
+    String source = handler.provider.sourceFiles[script].slowText();
     final int position = source.indexOf('main()');
     Expect.isTrue(position > 0, '$position > 0');
 
     var token;
 
     // When the cursor is at the same character offset as "main()", it
     // corresponds to having the cursor just before "main()". So we find the
     // "void" token.
     token = poi.findToken(element, position);
     Expect.isNotNull(token, 'token');
@@ skipping 18 matching lines @@
     token = poi.findToken(element, position + 5);
     Expect.isNotNull(token, 'token');
     Expect.equals(position + 4, token.charOffset, '$token');
     Expect.stringEquals('(', token.value);
   });
 }
 
 void main() {
   asyncTest(testPoi);
 }