Enables delegating signal strategy for It2Me Host.

remoting/signaling/xmpp_signal_strategy.cc

Index: remoting/signaling/xmpp_signal_strategy.cc
diff --git a/remoting/signaling/xmpp_signal_strategy.cc b/remoting/signaling/xmpp_signal_strategy.cc
index 46133761e1c44f34f7422e0cfbd35b86ec351c71..76c9566326b77b37f206318ea7f632a574c51759 100644
--- a/remoting/signaling/xmpp_signal_strategy.cc
+++ b/remoting/signaling/xmpp_signal_strategy.cc
@@ -164,6 +164,7 @@ XmppSignalStrategy::Core::Core(
   // Non-secure connections are allowed only for debugging.
   CHECK(xmpp_server_config_.use_tls);
 #endif
+  thread_checker_.DetachFromThread();

[Sergey Ulanov, 2016/10/05 21:49:07]

I don't think it's safe to detach from the thread here. Particularly
keep_alive_timer_ is initialized above and it gets attached to the current
thread, so SendKeepAlive() is called on the wrong thread. I would expect
DCHECK() in SendKeepAlive() fail as it would be called on the wrong thread.
Should be easy to fix by moving timer initialization to Connect().

[Sergey Ulanov, 2016/10/05 21:49:07]

Please add a comment xmpp_signal_strategy.h to make it clear that the class can
be created on a thread different from the one on which it's used.

[kelvinp, 2016/10/06 00:43:06]

Done.

[kelvinp, 2016/10/06 00:43:06]

Done.

 }
 
 XmppSignalStrategy::Core::~Core() {