Adding ElementEventStream.capture

tools/dom/src/EventStreamProvider.dart

Index: tools/dom/src/EventStreamProvider.dart
diff --git a/tools/dom/src/EventStreamProvider.dart b/tools/dom/src/EventStreamProvider.dart
index eef7ebdfda582cf88fe96a68d64e4605569e366d..58c6cde49c462eaff4c6e95eb840813e48c0edc9 100644
--- a/tools/dom/src/EventStreamProvider.dart
+++ b/tools/dom/src/EventStreamProvider.dart
@@ -40,6 +40,8 @@ abstract class ElementStream<T extends Event> implements Stream<T> {
    * [delegate](http://api.jquery.com/delegate/).
    */
   Stream<T> matches(String selector);
+
+  StreamSubscription<T> capture(void onData(T event));
 }
 
 /**
@@ -56,6 +58,10 @@ class _ElementEventStreamImpl<T extends Event> extends _EventStream<T>
         e._selector = selector;
         return e;
       });
+
+  StreamSubscription<T> capture(void onData(T event)) =>
+    new _EventStreamSubscription<T>(
+        this._target, this._eventType, onData, true);
 }
 
 /**
@@ -64,17 +70,12 @@ class _ElementEventStreamImpl<T extends Event> extends _EventStream<T>
  */
 class _ElementListEventStreamImpl<T extends Event> extends Stream<T>
     implements ElementStream<T> {
-  final _StreamPool _pool;
-  Stream<T> _stream;
-
-  _ElementListEventStreamImpl(targetList, eventType, useCapture) :
-      _pool = new _StreamPool.broadcast() {
-    for (Element target in targetList) {
-      var stream = new _EventStream(target, eventType, useCapture);
-      _pool.add(stream);
-    }
-    _stream = _pool.stream;
-  }
+  final Iterable<Element> _targetList;
+  final bool _useCapture;
+  final String _eventType;
+
+  _ElementListEventStreamImpl(
+      this._targetList, this._eventType, this._useCapture);
 
   Stream<T> matches(String selector) => this.where(
       (event) => event.target.matchesWithAncestors(selector)).map((e) {
@@ -82,16 +83,30 @@ class _ElementListEventStreamImpl<T extends Event> extends Stream<T>
         return e;
       });
 
-  // Delegate all regular Stream behavor to our wrapped Stream.
+  // Delegate all regular Stream behavior to a wrapped Stream.
   StreamSubscription<T> listen(void onData(T event),
       { Function onError,
         void onDone(),
-        bool cancelOnError}) =>
-      _stream.listen(onData, onError: onError, onDone: onDone,
+        bool cancelOnError}) {
+    var pool = new _StreamPool.broadcast();
+    for (var target in _targetList) {
+      pool.add(new _EventStream(target, _eventType, _useCapture));
+    }
+    return pool.stream.listen(onData, onError: onError, onDone: onDone,
           cancelOnError: cancelOnError);
+  }
+
+  StreamSubscription<T> capture(void onData(T event)) {
+    var pool = new _StreamPool.broadcast();
+    for (var target in _targetList) {
+      pool.add(new _EventStream(target, _eventType, true));
+    }
+    return pool.stream.listen(onData);
+  }
+
   Stream<T> asBroadcastStream({void onListen(StreamSubscription subscription),
                                void onCancel(StreamSubscription subscription)})
-      => _stream;
+      => this;
   bool get isBroadcast => true;
 }