--- old/src/jdk.incubator.httpclient/share/classes/jdk/incubator/http/WindowUpdateSender.java	2017-12-13 11:31:02.057055738 +0000
+++ new/src/jdk.incubator.httpclient/share/classes/jdk/incubator/http/WindowUpdateSender.java	2017-12-13 11:31:01.849060323 +0000
@@ -59,6 +59,8 @@
         //   or
         // - remaining window size reached max frame size.
         limit = Math.min(v0, v1);
+        debug.log(Level.DEBUG, "maxFrameSize=%d, initWindowSize=%d, limit=%d",
+                maxFrameSize, initWindowSize, limit);
     }
 
     abstract int getStreamId();