ipc: Make a common subclass for Channel and ProxyChannel.

ipc/ipc_endpoint.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 "ipc/ipc_endpoint.h"
+
+namespace IPC {
+
+Endpoint::Endpoint() : attachment_broker_endpoint_(false) {}
+
+void Endpoint::SetAttachmentBrokerEndpoint(bool is_endpoint) {
+  if (is_endpoint != attachment_broker_endpoint_) {
+    attachment_broker_endpoint_ = is_endpoint;
+    OnSetAttachmentBrokerEndpoint();
+  }
+}
+
+}  // namespace IPC