Compile several targets in Gallery in gyp v2.

ui/file_manager/externs/gallery_event.js

Index: ui/file_manager/externs/gallery_event.js
diff --git a/ui/file_manager/externs/gallery_event.js b/ui/file_manager/externs/gallery_event.js
new file mode 100644
index 0000000000000000000000000000000000000000..2c262ef6e8ce27ef1860b794f2eb66179b09760f
--- /dev/null
+++ b/ui/file_manager/externs/gallery_event.js
@@ -0,0 +1,20 @@
+// 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.
+
+
+/**
+ * @constructor
+ * @extends {Event}
+ */
+var GalleryEvent = function() {};
+
+/**
+ * @type {Entry}
+ */
+GalleryEvent.prototype.oldEntry;
+
+/**
+ * @type {GalleryItem}
+ */
+GalleryEvent.prototype.item;