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

remoting/host/win/wts_session_process_delegate.cc

Index: remoting/host/win/wts_session_process_delegate.cc
diff --git a/remoting/host/win/wts_session_process_delegate.cc b/remoting/host/win/wts_session_process_delegate.cc
index efdb8b85fbbde8a78ec4820af56543e78e08d88b..24c154ceeff5b82c81e033d2b98bb96977086b79 100644
--- a/remoting/host/win/wts_session_process_delegate.cc
+++ b/remoting/host/win/wts_session_process_delegate.cc
@@ -427,7 +427,7 @@ void WtsSessionProcessDelegate::Core::DoLaunchProcess() {
   pipe_ = std::move(pipe);
 
   IPC::AttachmentBroker::GetGlobal()->RegisterCommunicationChannel(
-      channel_.get());
+      channel_.get(), caller_task_runner_);

[Sergey Ulanov, 2016/03/17 23:41:56]

the channel_ is initialized with io_task_runner_ above. Should io_task_runner be
passed here as well?

[erikchen, 2016/03/19 00:52:46]

yes, done.

 
   // Report success if the worker process is lauched directly. Otherwise, PID of
   // the client connected to the pipe will be used later. See