ipc: Slight change to GetSenderWithProcessId().

ipc/attachment_broker_privileged.h

 // 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.
 
 #ifndef IPC_ATTACHMENT_BROKER_PRIVILEGED_H_
 #define IPC_ATTACHMENT_BROKER_PRIVILEGED_H_
 
 #include <vector>
 
 #include "base/memory/scoped_ptr.h"
@@ skipping 29 matching lines @@
   static void CreateBrokerIfNeeded();
 #endif  // defined(OS_MACOSX) && !defined(OS_IOS)
 
   // AttachmentBroker overrides.
   void RegisterCommunicationChannel(Endpoint* endpoint) override;
   void DeregisterCommunicationChannel(Endpoint* endpoint) override;
 
  protected:
   // Returns the sender whose peer's process id is |id|.
   // Returns nullptr if no sender is found.
+  // The lock returned by get_lock() must already be acquired before calling
+  // this method. The return value is only guaranteed to be valid while the lock
+  // is held.
   Sender* GetSenderWithProcessId(base::ProcessId id);
 
   // Errors that can be reported by subclasses.
   // These match tools/metrics/histograms.xml.
   // This enum is append-only.
   enum UMAError {
     // The brokerable attachment had a valid destination. This is the success
     // case.
     DESTINATION_FOUND = 0,
     // The brokerable attachment had a destination, but the broker did not have
@@ skipping 29 matching lines @@
   void LogError(UMAError error);
 
  private:
   std::vector<Endpoint*> endpoints_;
   DISALLOW_COPY_AND_ASSIGN(AttachmentBrokerPrivileged);
 };
 
 }  // namespace IPC
 
 #endif  // IPC_ATTACHMENT_BROKER_PRIVILEGED_H_