Revert "http2/h2demo: add HTTP/2 with Server Push"

Server Push is not more performant than regular HTTP/2 test
for this demo. I will produce a new demo page where Server Push
is clearly a better choice and consistently faster.

This reverts commit 3e967e1d.

Change-Id: Iace26e17714c0eca52785fc04d410df041e56415
Reviewed-on: https://go-review.googlesource.com/38608Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

http2/h2demo/h2demo.go

@@ -313,13 +313,6 @@ func newGopherTilesHandler() http.Handler {
 	}
 	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		ms, _ := strconv.Atoi(r.FormValue("latency"))
-		push, _ := strconv.ParseBool(r.FormValue("push"))
-
-		cacheBust := time.Now().UnixNano()
-		if push {
-			pushTiles(w, cacheBust, ms, xt, yt)
-		}
-
 		const nanosPerMilli = 1e6
 		if r.FormValue("x") != "" {
 			x, _ := strconv.Atoi(r.FormValue("x"))
@@ -336,13 +329,13 @@ func newGopherTilesHandler() http.Handler {
 		fmt.Fprintf(w, "A grid of %d tiled images is below. Compare:<p>", xt*yt)
 		for _, ms := range []int{0, 30, 200, 1000} {
 			d := time.Duration(ms) * nanosPerMilli
-			fmt.Fprintf(w, "[<a href='https://%s/gophertiles?latency=%d'>HTTP/2, %v latency</a>] [<a href='https://%s/gophertiles?latency=%d&push=true'>HTTP/2, %v latency with Server Push</a>] [<a href='http://%s/gophertiles?latency=%d'>HTTP/1, %v latency</a>]<br>\n",
-				httpsHost(), ms, d,
+			fmt.Fprintf(w, "[<a href='https://%s/gophertiles?latency=%d'>HTTP/2, %v latency</a>] [<a href='http://%s/gophertiles?latency=%d'>HTTP/1, %v latency</a>]<br>\n",
 				httpsHost(), ms, d,
 				httpHost(), ms, d,
 			)
 		}
 		io.WriteString(w, "<p>\n")
+		cacheBust := time.Now().UnixNano()
 		for y := 0; y < yt; y++ {
 			for x := 0; x < xt; x++ {
 				fmt.Fprintf(w, "<img width=%d height=%d src='/gophertiles?x=%d&y=%d&cachebust=%d&latency=%d'>",
@@ -363,21 +356,6 @@ function showtimes() {
 	})
 }
 
-func pushTiles(w http.ResponseWriter, cacheBust int64, latency int, xt, yt int) {
-	pusher, ok := w.(http.Pusher)
-	if !ok {
-		return
-	}
-	for y := 0; y < yt; y++ {
-		for x := 0; x < xt; x++ {
-			img := fmt.Sprintf("/gophertiles?x=%d&y=%d&cachebust=%d&latency=%d", x, y, cacheBust, latency)
-			if err := pusher.Push(img, nil); err != nil {
-				log.Printf("Failed to push %v: %v", img, err)
-			}
-		}
-	}
-}
-
 func httpsHost() string {
 	if *hostHTTPS != "" {
 		return *hostHTTPS