Mojo C++ bindings: support closing [Associated]InterfaceRequest with reason.

mojo/public/cpp/bindings/interface_request.h

Index: mojo/public/cpp/bindings/interface_request.h
diff --git a/mojo/public/cpp/bindings/interface_request.h b/mojo/public/cpp/bindings/interface_request.h
index fc23aec3ee73be187dabf450972a4a8906cf3626..5d75dd3e610deddefff8f773d348b4094eb76f09 100644
--- a/mojo/public/cpp/bindings/interface_request.h
+++ b/mojo/public/cpp/bindings/interface_request.h
@@ -5,12 +5,15 @@
 #ifndef MOJO_PUBLIC_CPP_BINDINGS_INTERFACE_REQUEST_H_
 #define MOJO_PUBLIC_CPP_BINDINGS_INTERFACE_REQUEST_H_
 
+#include <string>
 #include <utility>
 
 #include "base/macros.h"
 #include "base/single_thread_task_runner.h"
 #include "base/threading/thread_task_runner_handle.h"
 #include "mojo/public/cpp/bindings/interface_ptr.h"
+#include "mojo/public/cpp/bindings/lib/control_message_proxy.h"
+#include "mojo/public/cpp/system/message_pipe.h"
 
 namespace mojo {
 
@@ -64,6 +67,20 @@ class InterfaceRequest {
     return !is_pending() && !other.is_pending();
   }
 
+  void ResetWithReason(uint32_t custom_reason, const std::string& description) {
+    if (!handle_.is_valid())
+      return;
+
+    Message message =
+        internal::ControlMessageProxy::ConstructDisconnectReasonMessage(
+            custom_reason, description);
+    MojoResult result = WriteMessageNew(
+        handle_.get(), message.TakeMojoMessage(), MOJO_WRITE_MESSAGE_FLAG_NONE);
+    DCHECK_EQ(MOJO_RESULT_OK, result);
+
+    handle_.reset();
+  }
+
  private:
   ScopedMessagePipeHandle handle_;