http2: drop the gate type

Drop a trivial "gate" type used in exactly one location,
replacing it with an equivalent channel operation.

We've been using a "gate" with a different definition in
the quic package; dropping this hapax legomenon type from
the http2 package frees up the name if we want to use the
same gate here.

Change-Id: Id9c7d05daf7ee920c38090df960822fcc1168a4d
Reviewed-on: https://go-review.googlesource.com/c/net/+/584896
Reviewed-by: Jonathan Amsterdam <[email protected]>
LUCI-TryBot-Result: Go LUCI <[email protected]>

Author: neild

http2/http2.go

@@ -210,12 +210,6 @@ type stringWriter interface {
 	WriteString(s string) (n int, err error)
 }
 
-// A gate lets two goroutines coordinate their activities.
-type gate chan struct{}
-
-func (g gate) Done() { g <- struct{}{} }
-func (g gate) Wait() { <-g }
-
 // A closeWaiter is like a sync.WaitGroup but only goes 1 to 0 (open to closed).
 type closeWaiter chan struct{}
 

http2/server.go

@@ -811,8 +811,8 @@ type readFrameResult struct {
 // consumer is done with the frame.
 // It's run on its own goroutine.
 func (sc *serverConn) readFrames() {
-	gate := make(gate)
-	gateDone := gate.Done
+	gate := make(chan struct{})
+	gateDone := func() { gate <- struct{}{} }
 	for {
 		f, err := sc.framer.ReadFrame()
 		select {