Create an apptesting framework for dart.

mojo/public/dart/src/application.dart

Index: mojo/public/dart/src/application.dart
diff --git a/mojo/public/dart/src/application.dart b/mojo/public/dart/src/application.dart
index 6e61df68c8f9bd2547b9c54ad04c3c8bb79687fe..671ef29c11b68881f2ad5f29bc5ba4f9f55ba0ce 100644
--- a/mojo/public/dart/src/application.dart
+++ b/mojo/public/dart/src/application.dart
@@ -98,6 +98,13 @@ abstract class Application {
     _applicationImpl.close();
   }
 
+  // This method closes all the application connections. Used during apptesting.
+  resetConnections() {
+    assert(_applicationImpl != null);
+    _applicationConnections.forEach((c) => c.close());
+    _applicationConnections.clear();
+  }
+
   void _acceptConnection(String requestorUrl, ServiceProviderStub services,
       ServiceProviderProxy exposedServices, String resolvedUrl) {
     var connection = new ApplicationConnection(services, exposedServices);