Add UMA metrics to log attachment broker errors.

ipc/attachment_broker_privileged.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/attachment_broker_privileged.h"
 
 #include <algorithm>
 
+#include "base/metrics/histogram.h"
 #include "ipc/ipc_endpoint.h"
 
 namespace IPC {
 
 AttachmentBrokerPrivileged::AttachmentBrokerPrivileged() {}
 
 AttachmentBrokerPrivileged::~AttachmentBrokerPrivileged() {}
 
 void AttachmentBrokerPrivileged::RegisterCommunicationChannel(
     Endpoint* endpoint) {
@@ skipping 11 matching lines @@
 }
 
 Sender* AttachmentBrokerPrivileged::GetSenderWithProcessId(base::ProcessId id) {
   auto it = std::find_if(endpoints_.begin(), endpoints_.end(),
                          [id](Endpoint* c) { return c->GetPeerPID() == id; });
   if (it == endpoints_.end())
     return nullptr;
   return *it;
 }
 
+void AttachmentBrokerPrivileged::LogError(UMAError error) {
+  UMA_HISTOGRAM_ENUMERATION(
+      "IPC.AttachmentBrokerPrivileged.BrokerAttachmentError", error, MAX_VALUE);
+}
+
 }  // namespace IPC