ipc: Move methods into AttachmentBroker interface.

ipc/attachment_broker.cc

Index: ipc/attachment_broker.cc
diff --git a/ipc/attachment_broker.cc b/ipc/attachment_broker.cc
index dac046b453a00edb8d2dbb555996fe29229bb3cb..ba1a6cb4eff5237b3d6374720e360b9fc3da7192 100644
--- a/ipc/attachment_broker.cc
+++ b/ipc/attachment_broker.cc
@@ -25,7 +25,12 @@ AttachmentBroker* AttachmentBroker::GetGlobal() {
   return g_attachment_broker;
 }
 
+#if defined(OS_MACOSX) && !defined(OS_IOS)
+AttachmentBroker::AttachmentBroker() : port_provider_(nullptr) {}
+#else
 AttachmentBroker::AttachmentBroker() {}
+#endif  // defined(OS_MACOSX) && !defined(OS_IOS)
+
 AttachmentBroker::~AttachmentBroker() {}
 
 bool AttachmentBroker::GetAttachmentWithId(
@@ -54,6 +59,14 @@ void AttachmentBroker::RemoveObserver(AttachmentBroker::Observer* observer) {
     observers_.erase(it);
 }
 
+void AttachmentBroker::RegisterCommunicationChannel(Endpoint* endpoint) {
+  NOTREACHED();
+}
+
+void AttachmentBroker::DeregisterCommunicationChannel(Endpoint* endpoint) {
+  NOTREACHED();
+}
+
 void AttachmentBroker::HandleReceivedAttachment(
     const scoped_refptr<BrokerableAttachment>& attachment) {
   attachments_.push_back(attachment);