xP: fix alternative browsers on iOS

As a rule, they use the same stupid and broken WebKit.

xP/xP.go

@@ -176,9 +176,11 @@ func handleWS(w http.ResponseWriter, r *http.Request) {
 	}
 
 	// AppleWebKit can be broken with compression.
-	if agent := r.UserAgent(); strings.Contains(agent, " Version/") &&
-		(strings.HasPrefix(agent, "Mozilla/5.0 (Macintosh; ") ||
-			strings.HasPrefix(agent, "Mozilla/5.0 (iPhone; ")) {
+	// It would be more reliable to check for 'ApplePaySession' in window in JS,
+	// and have us disable compression based on a query parameter.
+	if agent := r.UserAgent(); (strings.Contains(agent, " Version/") &&
+		strings.HasPrefix(agent, "Mozilla/5.0 (Macintosh; ")) ||
+		strings.HasPrefix(agent, "Mozilla/5.0 (iPhone; ") {
 		opts.CompressionMode = websocket.CompressionDisabled
 	}