fix broadcast streams

pkg/analyzer/lib/src/generated/engine.dart

Index: pkg/analyzer/lib/src/generated/engine.dart
diff --git a/pkg/analyzer/lib/src/generated/engine.dart b/pkg/analyzer/lib/src/generated/engine.dart
index 3195e89e3de68b893c1daac28fc31b0de6660afd..958fda62caa244069fef8740de01e62fdadd2865 100644
--- a/pkg/analyzer/lib/src/generated/engine.dart
+++ b/pkg/analyzer/lib/src/generated/engine.dart
@@ -989,12 +989,6 @@ class AnalysisContextImpl implements InternalAnalysisContext {
   StreamController<SourcesChangedEvent> _onSourcesChangedController;
 
   /**
-   * The stream that is notified when sources have been added or removed,
-   * or the source's content has changed.
-   */
-  Stream<SourcesChangedEvent> _onSourcesChanged;
-
-  /**
    * The listeners that are to be notified when various analysis results are produced in this
    * context.
    */
@@ -1010,8 +1004,8 @@ class AnalysisContextImpl implements InternalAnalysisContext {
         AnalysisOptionsImpl.DEFAULT_CACHE_SIZE,
         new AnalysisContextImpl_ContextRetentionPolicy(this));
     _cache = createCacheFromSourceFactory(null);
-    _onSourcesChangedController = new StreamController<SourcesChangedEvent>();
-    _onSourcesChanged = _onSourcesChangedController.stream.asBroadcastStream();
+    _onSourcesChangedController =
+        new StreamController<SourcesChangedEvent>.broadcast();
   }
 
   @override
@@ -1239,7 +1233,8 @@ class AnalysisContextImpl implements InternalAnalysisContext {
   }
 
   @override
-  Stream<SourcesChangedEvent> get onSourcesChanged => _onSourcesChanged;
+  Stream<SourcesChangedEvent> get onSourcesChanged =>
+      _onSourcesChangedController.stream;
 
   @override
   List<Source> get prioritySources => _priorityOrder;