Make the mapping from client id -> secret asynchronous.

remoting/protocol/negotiating_authenticator_base.cc

Index: remoting/protocol/negotiating_authenticator_base.cc
diff --git a/remoting/protocol/negotiating_authenticator_base.cc b/remoting/protocol/negotiating_authenticator_base.cc
index 2c2b4c5216291b9e159f8b67b495c6c5f5223f7b..30bd8ba750d54e2fd59fc1f987e6ba6ea6aef896 100644
--- a/remoting/protocol/negotiating_authenticator_base.cc
+++ b/remoting/protocol/negotiating_authenticator_base.cc
@@ -52,6 +52,7 @@ void NegotiatingAuthenticatorBase::ProcessMessageInternal(
     // If the message was not discarded and the authenticator is waiting for it,
     // give it to the underlying authenticator to process.
     // |current_authenticator_| is owned, so Unretained() is safe here.
+    state_ = PROCESSING_MESSAGE;
     current_authenticator_->ProcessMessage(message, base::Bind(
         &NegotiatingAuthenticatorBase::UpdateState,
         base::Unretained(this), resume_callback));