Add reprioritization to socket pools.

net/http/http_stream_factory_impl_job.cc

Index: net/http/http_stream_factory_impl_job.cc
diff --git a/net/http/http_stream_factory_impl_job.cc b/net/http/http_stream_factory_impl_job.cc
index 375a71b9d3c5d208a7f573674fb410f542ac1141..c6289680a53fc730a8dd192610da2129218ecdbb 100644
--- a/net/http/http_stream_factory_impl_job.cc
+++ b/net/http/http_stream_factory_impl_job.cc
@@ -318,8 +318,18 @@ void HttpStreamFactoryImpl::Job::Orphan() {
 
 void HttpStreamFactoryImpl::Job::SetPriority(RequestPriority priority) {
   priority_ = priority;
-  // TODO(akalin): Propagate this to |connection_| and maybe the
-  // preconnect state.
+  // Ownership of |connection_| is passed to the newly created stream
+  // or H2 session in DoCreateStream(), and the consumer is not
+  // notified immediately, so this call may occur when |connection_|
+  // is null.
+  //
+  // Note that streams are created without a priority associated with them,
+  // and it is up to the consumer to set their priority via
+  // HttpStream::InitializeStream().  So there is no need for this code
+  // to propagate priority changes to the newly created stream.
+  if (connection_ && connection_->is_initialized())
+    connection_->SetPriority(priority);
+  // TODO(akalin): Maybe Propagate this to the preconnect state.
 }
 
 bool HttpStreamFactoryImpl::Job::was_alpn_negotiated() const {