Mojo C++ bindings: Simplify associated interface API.

mojo/public/cpp/bindings/lib/binding_state.cc

Index: mojo/public/cpp/bindings/lib/binding_state.cc
diff --git a/mojo/public/cpp/bindings/lib/binding_state.cc b/mojo/public/cpp/bindings/lib/binding_state.cc
index c98fc6fec8707d22a8c0ef152dadc45e98c9e71b..b34cb47e289c754f229879ca5f8016b5bcedfd32 100644
--- a/mojo/public/cpp/bindings/lib/binding_state.cc
+++ b/mojo/public/cpp/bindings/lib/binding_state.cc
@@ -4,8 +4,6 @@
 
 #include "mojo/public/cpp/bindings/lib/binding_state.h"
 
-#include "mojo/public/cpp/bindings/lib/control_message_proxy.h"
-
 namespace mojo {
 namespace internal {
 
@@ -54,7 +52,7 @@ void BindingStateBase::CloseWithReason(uint32_t custom_reason,
 }
 
 void BindingStateBase::FlushForTesting() {
-  endpoint_client_->control_message_proxy()->FlushForTesting();
+  endpoint_client_->FlushForTesting();
 }
 
 void BindingStateBase::EnableTestingMode() {