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 3ae900b5ce884a95669d031425ee1b1cc07ccf07..fd7dc6014f749b7d16959f96abe9e20e0841f5a6 100644
--- a/mojo/public/dart/src/application.dart
+++ b/mojo/public/dart/src/application.dart
@@ -95,6 +95,13 @@ 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) {
     var connection = new ApplicationConnection(services, exposedServices);