add sdkPath and enable tests

pkg/analysis_server/lib/src/domain_context.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.
 
 library domain.context;
 
 import 'package:analysis_server/src/analysis_server.dart';
 import 'package:analysis_server/src/protocol.dart';
 import 'package:analyzer/src/generated/engine.dart';
 import 'package:analyzer/src/generated/source.dart';
@@ skipping 108 matching lines @@
     context.applyChanges(changeSet);
     Response response = new Response(request.id);
     return response;
   }
 
   /**
    * Convert the given JSON object into a [ChangeSet].
    */
   ChangeSet createChangeSet(Map<String, Object> jsonData) {
     // TODO(brianwilkerson) Implement this.
-    return null;
+    return new ChangeSet();
   }
 
   /**
    * Set the options controlling analysis within a context to the given set of
    * options.
    */
   Response setOptions(Request request) {
     AnalysisContext context = getAnalysisContext(request);
 
     context.analysisOptions = createAnalysisOptions(request);
@@ skipping 61 matching lines @@
    */
   AnalysisContext getAnalysisContext(Request request) {
     String contextId = request.getRequiredParameter(CONTEXT_ID_PARAM);
     AnalysisContext context = server.contextMap[contextId];
     if (context == null) {
       throw new RequestFailure(new Response.contextDoesNotExist(request));
     }
     return context;
   }
 }