Server push cancellation: add NetLogs to track cache lookup transaction

net/spdy/spdy_session.cc

Index: net/spdy/spdy_session.cc
diff --git a/net/spdy/spdy_session.cc b/net/spdy/spdy_session.cc
index a7287cdecf96f9740a1e0e9f89c7f8de61049758..245fbbe8a0d84a5ab5978b6ca37f1e58d5a0e071 100644
--- a/net/spdy/spdy_session.cc
+++ b/net/spdy/spdy_session.cc
@@ -360,7 +360,7 @@ class SpdyServerPushHelper : public ServerPushDelegate::ServerPushHelper {
       session_->CancelPush(request_url_);
   }
 
-  const GURL& GetURL() override { return request_url_; }
+  const GURL& GetURL() const override { return request_url_; }
 
  private:
   base::WeakPtr<SpdySession> session_;
@@ -2693,7 +2693,8 @@ void SpdySession::TryCreatePushStream(SpdyStreamId stream_id,
   // Notify the push_delegate that a push promise has been received.
   if (push_delegate_) {
     push_delegate_->OnPush(base::MakeUnique<SpdyServerPushHelper>(
-        weak_factory_.GetWeakPtr(), gurl));
+                               weak_factory_.GetWeakPtr(), gurl),
+                           net_log_);
   }
 
   active_it->second->OnPushPromiseHeadersReceived(std::move(headers));