Nit comments about other parts of the OpenJDK 9 HTTP Client AP.

Should the Runnables passed to the Executor perhaps override toString() (to
help figure out during debugging what is running on the Executor and why)?


This issue has been filed to capture comments raised by tobiast at google dot com, see
http://mail.openjdk.java.net/pipermail/net-dev/2017-July/010872.html