Fix try/poi.

pkg/dart2js_incremental/lib/caching_compiler.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.
 
 part of dart2js_incremental;
 
 /// Do not call this method directly. It will be made private.
 // TODO(ahe): Make this method private.
 Future<Compiler> reuseCompiler(
     {CompilerDiagnostics diagnosticHandler,
@@ skipping 10 matching lines @@
   if (libraryRoot == null) {
     throw 'Missing libraryRoot';
   }
   if (inputProvider == null) {
     throw 'Missing inputProvider';
   }
   if (diagnosticHandler == null) {
     throw 'Missing diagnosticHandler';
   }
   if (outputProvider == null) {
-    outputProvider = NullSink.outputProvider;
+    outputProvider = const NullCompilerOutput();
   }
   if (environment == null) {
     environment = {};
   }
   Compiler compiler = cachedCompiler;
   if (compiler == null ||
       compiler.libraryRoot != libraryRoot ||
       !compiler.hasIncrementalSupport ||
       compiler.hasCrashed ||
       compiler.enqueuer.resolution.hasEnqueuedReflectiveElements ||
@@ skipping 147 matching lines @@
   final Map<String, String> output = new Map<String, String>();
 
   EventSink<String> call(String name, String extension) {
     return new StringEventSink((String data) {
       output['$name.$extension'] = data;
     });
   }
 
   String operator[] (String key) => output[key];
 }