Move flush back into synchronized output.

lib/protocol/http2/connection.rb

@@ -215,20 +215,20 @@ def receive_goaway(frame)
 			def write_frame(frame)
 				synchronize do
 					@framer.write_frame(frame)
+
+					# I tried moving this outside the synchronize block but it caused a deadlock.
+					@framer.flush
 				end
-
-				# The IO is already synchronized, and we don't want additional contention.
-				@framer.flush
 			end
 
 			def write_frames
 				if @framer
 					synchronize do
 						yield @framer
+
+						# See note above.
+						@framer.flush
 					end
-
-					# See above note.
-					@framer.flush
 				else
 					raise EOFError, "Connection closed!"
 				end