Fix incremental 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 117 matching lines @@
 
     backend.emitter.readTypeVariables.clear();
 
     backend.emitter.oldEmitter
         ..outputBuffers.clear()
         ..isolateProperties = null
         ..classesCollector = null
         ..mangledFieldNames.clear()
         ..mangledGlobalFieldNames.clear()
         ..recordedMangledNames.clear()
-        ..additionalProperties.clear()
         ..clearCspPrecompiledNodes()
         ..elementDescriptors.clear();
 
     backend.emitter
         ..nativeClassesAndSubclasses.clear()
         ..outputContainsConstantList = false
         ..neededClasses.clear()
         ..outputClassLists.clear()
         ..outputConstantLists.clear()
         ..outputStaticLists.clear()
@@ skipping 47 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];
 }