Add FlushForTesting to InterfacePtr and Binding.

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

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "mojo/public/cpp/bindings/lib/control_message_handler.h"
 
 #include <stddef.h>
 #include <stdint.h>
 #include <utility>
 
@@ skipping 43 matching lines @@
           message->mutable_payload());
   interface_control::RunMessageParamsPtr params_ptr;
   Deserialize<interface_control::RunMessageParamsDataView>(params, &params_ptr,
                                                            &context_);
   auto& input = *params_ptr->input;
   interface_control::RunOutputPtr output = interface_control::RunOutput::New();
   if (input.is_query_version()) {
     output->set_query_version_result(
         interface_control::QueryVersionResult::New());
     output->get_query_version_result()->version = interface_version_;
+  } else if (input.is_flush_for_testing()) {
+    output.reset();
   } else {
     output.reset();
   }
 
   auto response_params_ptr = interface_control::RunResponseMessageParams::New();
   response_params_ptr->output = std::move(output);
   size_t size =
       PrepareToSerialize<interface_control::RunResponseMessageParamsDataView>(
           response_params_ptr, &context_);
   ResponseMessageBuilder builder(interface_control::kRunMessageId, size,
@@ skipping 20 matching lines @@
       params, &params_ptr, &context_);
   auto& input = *params_ptr->input;
   if (input.is_require_version())
     return interface_version_ >= input.get_require_version()->version;
 
   return false;
 }
 
 }  // namespace internal
 }  // namespace mojo