Clarify what _outgoing_app_size counts in sslproto comments

Author: gpshead

Lib/asyncio/sslproto.py

@@ -308,7 +308,8 @@ def __init__(self, loop, app_protocol, sslcontext, waiter,
         # App data write buffering
         self._write_backlog = collections.deque()
         self._write_buffer_size = 0
-        # How much of self._outgoing is encrypted app data
+        # How much of self._outgoing was produced by _do_write(): encrypted
+        # app data, plus anything else OpenSSL flushed along with it
         self._outgoing_app_size = 0
 
         self._waiter = waiter
@@ -902,9 +903,10 @@ def _control_ssl_reading(self):
         # Also count the records OpenSSL writes on its own while reading
         # (alerts, KeyUpdate replies, ...) which the peer does not read:
         # the app is not involved in producing them, so pausing it does
-        # not bound them; only pausing reads from the peer does.  App data
-        # is left out so that two peers which both write before they read
-        # cannot deadlock.
+        # not bound them; only pausing reads from the peer does.  Whatever
+        # was produced while writing app data (_outgoing_app_size) is left
+        # out so that two peers which both write before they read cannot
+        # deadlock.
         size = (self._get_read_buffer_size() +
                 self._outgoing.pending - self._outgoing_app_size)
         if size >= self._incoming_high_water and not self._ssl_reading_paused: