Compile more targets in foreground/js/ui in gyp v2 (3)

ui/file_manager/externs/drag_target.js

+// Copyright 2017 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+/**
+ * @interface
+ */
+function DragTarget(){};
+
+/**
+ * This definition is required to satisfy
+ * ui/file_manager/file_manager/foreground/js/ui/drag_selector.js.
+ *
+ * @param {number} x
+ * @param {number} y
+ * @param {number=} opt_width
+ * @param {number=} opt_height
+ * @return {Array<number>}
+ */
+DragTarget.prototype.getHitElements = function(x, y, opt_width, opt_height) {};