Add FlushForTesting to InterfacePtr and Binding.

mojo/public/cpp/bindings/interface_ptr.h

Index: mojo/public/cpp/bindings/interface_ptr.h
diff --git a/mojo/public/cpp/bindings/interface_ptr.h b/mojo/public/cpp/bindings/interface_ptr.h
index edcb9bf2baf656ee80e10d585729409d4a16c1df..1a133fa3d833d6cd5aa5ddae4763c9c9033f877d 100644
--- a/mojo/public/cpp/bindings/interface_ptr.h
+++ b/mojo/public/cpp/bindings/interface_ptr.h
@@ -114,6 +114,12 @@ class InterfacePtr {
     internal_state_.RequireVersion(version);
   }
 
+  // Sends a no-op message on the underlying message pipe and runs the current
+  // message loop until its response is received. This can be used in tests to
+  // verify that no message was sent on a message pipe in response to some
+  // stimulus.
+  void FlushForTesting() { internal_state_.FlushForTesting(); }
+
   // Closes the bound message pipe (if any) and returns the pointer to the
   // unbound state.
   void reset() {