Avoid setting a duplicate SpdySessionKey on a Request

net/http/http_stream_factory_impl_request.cc

Index: net/http/http_stream_factory_impl_request.cc
diff --git a/net/http/http_stream_factory_impl_request.cc b/net/http/http_stream_factory_impl_request.cc
index c8924d25ad962f5ad064b57a1a6c4fb2e95d08e0..2cc497f2112371b1d80ed5d40f23cb9346076f49 100644
--- a/net/http/http_stream_factory_impl_request.cc
+++ b/net/http/http_stream_factory_impl_request.cc
@@ -54,7 +54,7 @@ HttpStreamFactoryImpl::Request::~Request() {
 
 void HttpStreamFactoryImpl::Request::SetSpdySessionKey(
     const SpdySessionKey& spdy_session_key) {
-  DCHECK(!spdy_session_key_.get());
+  CHECK(!spdy_session_key_.get());
   spdy_session_key_.reset(new SpdySessionKey(spdy_session_key));
   RequestSet& request_set =
       factory_->spdy_session_request_map_[spdy_session_key];
@@ -250,6 +250,10 @@ HttpStreamFactoryImpl::Request::RemoveRequestFromSpdySessionRequestMap() {
   }
 }
 
+bool HttpStreamFactoryImpl::Request::HasSpdySessionKey() const {
+  return spdy_session_key_.get() != NULL;
+}
+
 // TODO(jgraettinger): Currently, HttpStreamFactoryImpl::Job notifies a
 // Request that the session is ready, which in turn notifies it's delegate,
 // and then it notifies HttpStreamFactoryImpl so that /other/ requests may