Dart: Simplifies the handle watcher. Various cleanups and bugfixes.

mojo/dart/test/bindings_generation_test.dart

Index: mojo/dart/test/bindings_generation_test.dart
diff --git a/mojo/dart/test/bindings_generation_test.dart b/mojo/dart/test/bindings_generation_test.dart
index e2cefb345c597b1891b6deb4580575e453c44793..7518a493b65366c3647125363031385cb210fafa 100644
--- a/mojo/dart/test/bindings_generation_test.dart
+++ b/mojo/dart/test/bindings_generation_test.dart
@@ -18,26 +18,26 @@ class ProviderImpl extends sample.ProviderInterface {
   echoString(String a) {
     var response = new sample.Provider_EchoString_ResponseParams();
     response.a = a;
-    return response;
+    return new Future.value(response);
   }
 
   echoStrings(String a, String b) {
     var response = new sample.Provider_EchoStrings_ResponseParams();
     response.a = a;
     response.b = b;
-    return response;
+    return new Future.value(response);
   }
 
   echoMessagePipeHanlde(core.RawMojoHandle a) {
     var response = new sample.Provider_EchoMessagePipeHandle_ResponseParams();
     response.a = a;
-    return response;
+    return new Future.value(response);
   }
 
   echoEnum(int a) {
     var response = new sample.Provider_EchoEnum_ResponseParams();
     response.a = a;
-    return response;
+    return new Future.value(response);
   }
 }