Dart: Removes need to call listen().

mojo/public/dart/src/event_stream.dart

Index: mojo/public/dart/src/event_stream.dart
diff --git a/mojo/public/dart/src/event_stream.dart b/mojo/public/dart/src/event_stream.dart
index 9c8321709332fe05ab77edf1ca35dabf13b2dba9..268a5d431adce7135dc878ba117af3c93ecbb9c2 100644
--- a/mojo/public/dart/src/event_stream.dart
+++ b/mojo/public/dart/src/event_stream.dart
@@ -124,7 +124,7 @@ class MojoEventStream extends Stream<List<int>> {
 }
 
 abstract class Listener {
-  StreamSubscription<List<int>> listen({Function onClosed});
+  StreamSubscription<List<int>> listen();
 }
 
 class MojoEventStreamListener {
@@ -133,25 +133,20 @@ class MojoEventStreamListener {
   bool _isOpen = false;
   bool _isInHandler = false;
   StreamSubscription subscription;
+  Function _onError;
 
-  MojoEventStreamListener.fromEndpoint(MojoMessagePipeEndpoint endpoint,
-      {bool doListen: true, Function onClosed})
+  MojoEventStreamListener.fromEndpoint(MojoMessagePipeEndpoint endpoint)
       : _endpoint = endpoint,
         _eventStream = new MojoEventStream(endpoint.handle),
         _isOpen = false {
-    if (doListen) {
-      listen(onClosed: onClosed);
-    }
+    listen();
   }
 
-  MojoEventStreamListener.fromHandle(MojoHandle handle, {bool doListen: true,
-      Function onClosed}) {
+  MojoEventStreamListener.fromHandle(MojoHandle handle) {
     _endpoint = new MojoMessagePipeEndpoint(handle);
     _eventStream = new MojoEventStream(handle);
     _isOpen = false;
-    if (doListen) {
-      listen(onClosed: onClosed);
-    }
+    listen();
   }
 
   MojoEventStreamListener.unbound()
@@ -173,14 +168,14 @@ class MojoEventStreamListener {
     _isOpen = false;
   }
 
-  StreamSubscription<List<int>> listen({Function onClosed}) {
+  StreamSubscription<List<int>> listen() {
     assert(isBound && (subscription == null));
     _isOpen = true;
     subscription = _eventStream.listen((List<int> event) {
       var signalsWatched = new MojoHandleSignals(event[0]);
       var signalsReceived = new MojoHandleSignals(event[1]);
       if (signalsReceived.isPeerClosed) {
-        if (onClosed != null) onClosed();
+        if (onError != null) onError();
         close();
         // The peer being closed obviates any other signal we might
         // have received since we won't be able to read or write the handle.
@@ -217,6 +212,21 @@ class MojoEventStreamListener {
   void handleRead() {}
   void handleWrite() {}
 
+  Function get onError => _onError;
+           set onError(Function f) {
+    if (f == null) {
+      _onError = null;
+    } else {
+      Function cachedOnError = _onError;

[hansmuller1, 2015/03/05 00:35:32]

Why are we accumulating onError functions here? Developers who really want to
wrap the value of onError can easily do so, doing it automatically seems like it
would lead to confusion.

[zra, 2015/03/05 16:39:29]

I was worried about people accidentally overwriting the onError callbacks added
for closing ApplicationConnection and LocalServiceProvider, but I can try to
work around that a different way. I'll write it up and see what it looks like.

+      _onError = (() {
+        if (cachedOnError != null) {
+          cachedOnError();
+        }
+        f();
+      });
+    }
+  }
+
   MojoMessagePipeEndpoint get endpoint => _endpoint;
   bool get isOpen => _isOpen;
   bool get isInHandler => _isInHandler;