http: remove unused code block

fix #7769

Signed-off-by: Fedor Indutny <fedor@indutny.com>

lib/_http_server.js

@@ -187,30 +187,15 @@ ServerResponse.prototype.writeHead = function(statusCode) {
 
   var obj = arguments[headerIndex];
 
-  if (obj && this._headers) {
-    if (util.isArray(obj)) {
-      // handle array case
-      // TODO: remove when array is no longer accepted
-      var field;
-      for (var i = 0, len = obj.length; i < len; ++i) {
-        field = obj[i][0];
-        if (!util.isUndefined(headers[field])) {
-          obj.push([field, headers[field]]);
-        }
-      }
-      headers = obj;
-
-    } else {
-      // handle object case
+  if (this._headers) {
+    // Slow-case: when progressive API and header fields are passed.
+    if (obj) {
       var keys = Object.keys(obj);
       for (var i = 0; i < keys.length; i++) {
         var k = keys[i];
         if (k) this.setHeader(k, obj[k]);
       }
-      // Slow-case: when progressive API and header fields are passed.
-      headers = this._renderHeaders();
     }
-  } else if (this._headers) {
     // only progressive api is used
     headers = this._renderHeaders();
   } else {