Fix typo in caching compiler.

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(
     {DiagnosticHandler diagnosticHandler,
@@ skipping 69 matching lines @@
           compiler.enqueuer.resolution, compiler.globalDependencies);
       return compiler;
     });
   } else {
     for (final task in compiler.tasks) {
       if (task.watch != null) {
         task.watch.reset();
       }
     }
     compiler
-        ..outputProvider = outputProvider
+        ..userOutputProvider = outputProvider
         ..provider = inputProvider
         ..handler = diagnosticHandler
         ..enqueuer.resolution.queueIsClosed = false
         ..enqueuer.resolution.hasEnqueuedReflectiveElements = false
         ..enqueuer.resolution.hasEnqueuedReflectiveStaticFields = false
         ..enqueuer.codegen.queueIsClosed = false
         ..enqueuer.codegen.hasEnqueuedReflectiveElements = false
         ..enqueuer.codegen.hasEnqueuedReflectiveStaticFields = false
         ..compilationFailed = false;
     JavaScriptBackend backend = compiler.backend;
@@ skipping 99 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];
 }