Revert of [mojo-bindings] Use Watch API instead of MessagePumpMojo

mojo/shell/tests/connect/connect_test_app.cc

Index: mojo/shell/tests/connect/connect_test_app.cc
diff --git a/mojo/shell/tests/connect/connect_test_app.cc b/mojo/shell/tests/connect/connect_test_app.cc
index 96c9b1de096e8afb211d0d2cdc8aa038a85539c5..5081c8bd0464c8d0ce1521a3821c3319551c3967 100644
--- a/mojo/shell/tests/connect/connect_test_app.cc
+++ b/mojo/shell/tests/connect/connect_test_app.cc
@@ -110,13 +110,7 @@
     test_service->GetTitle(
         base::Bind(&ConnectTestApp::OnGotTitle, base::Unretained(this),
                    callback, &run_loop));
-    {
-      // This message is dispatched as a task on the same run loop, so we need
-      // to allow nesting in order to pump additional signals.
-      base::MessageLoop::ScopedNestableTaskAllower allow(
-          base::MessageLoop::current());
-      run_loop.Run();
-    }
+    run_loop.Run();
   }
 
   // test::mojom::BlockedInterface: