Add support for Attachment Brokering of IPC::Channels on multiple threads.

ipc/attachment_broker.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_H_
 #define IPC_ATTACHMENT_BROKER_H_
 
 #include "base/gtest_prod_util.h"
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
 #include "base/process/process_handle.h"
 #include "base/synchronization/lock.h"
 #include "build/build_config.h"
 #include "ipc/brokerable_attachment.h"
 #include "ipc/ipc_export.h"
 #include "ipc/ipc_listener.h"
 
 // If the platform has no attachments that need brokering, then it shouldn't
 // compile any code that calls member functions of AttachmentBroker. This
 // prevents symbols only used by AttachmentBroker and its subclasses from
 // making it into the binary.
 #if defined(OS_WIN) || (defined(OS_MACOSX) && !defined(OS_IOS))
 #define USE_ATTACHMENT_BROKER 1
 #else
 #define USE_ATTACHMENT_BROKER 0
 #endif  // defined(OS_WIN)
 
 namespace base {
 class SequencedTaskRunner;
+class SingleThreadTaskRunner;
 };
 
 namespace IPC {
 
 class AttachmentBroker;
 class Endpoint;
 
 // Classes that inherit from this abstract base class are capable of
 // communicating with a broker to send and receive attachments to Chrome IPC
 // messages.
@@ skipping 47 matching lines @@
   void AddObserver(Observer* observer,
                    const scoped_refptr<base::SequencedTaskRunner>& runner);
   void RemoveObserver(Observer* observer);
 
   // These two methods should only be called by the broker process.
   //
   // Each unprivileged process should have one IPC channel on which it
   // communicates attachment information with the broker process. In the broker
   // process, these channels must be registered and deregistered with the
   // Attachment Broker as they are created and destroyed.
-  virtual void RegisterCommunicationChannel(Endpoint* endpoint);
+  //
+  // Invocations of Send() on |endpoint| will occur on thread bound to |runner|.
+  virtual void RegisterCommunicationChannel(
+      Endpoint* endpoint,
+      scoped_refptr<base::SingleThreadTaskRunner> runner);
   virtual void DeregisterCommunicationChannel(Endpoint* endpoint);
 
   // In each unprivileged process, exactly one channel should be used to
   // communicate brokerable attachments with the broker process.
   virtual void RegisterBrokerCommunicationChannel(Endpoint* endpoint);
   virtual void DeregisterBrokerCommunicationChannel(Endpoint* endpoint);
 
   // True if and only if this broker is privileged.
   virtual bool IsPrivilegedBroker();
 
@@ skipping 50 matching lines @@
 
   // The AttachmentBroker can be accessed from any thread, so modifications to
   // internal state must be guarded by a lock.
   base::Lock lock_;
   DISALLOW_COPY_AND_ASSIGN(AttachmentBroker);
 };
 
 }  // namespace IPC
 
 #endif  // IPC_ATTACHMENT_BROKER_H_