Files app: Move common/js/externs.js to externs/*.

ui/file_manager/externs/background_window.js

Index: ui/file_manager/externs/background_window.js
diff --git a/ui/file_manager/externs/background_window.js b/ui/file_manager/externs/background_window.js
new file mode 100644
index 0000000000000000000000000000000000000000..e6e8322b79471ca937faf093abdae9c0c88bf319
--- /dev/null
+++ b/ui/file_manager/externs/background_window.js
@@ -0,0 +1,28 @@
+// Copyright 2016 The Chromium Authors. All rights reserved.

[oka, 2016/12/26 08:13:05]

nit: You may want to set similarity=20 or something on git cl upload so that
it's detected that this code is moved from externs.js.

[fukino, 2016/12/26 08:28:15]

Done.

+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+/**
+ * @constructor
+ * @extends {Window}
+ */
+var BackgroundWindow = function() {};
+
+/**
+ * @type {FileBrowserBackground}
+ */
+BackgroundWindow.prototype.background;
+
+/**
+ * @param {Window} window
+ */
+BackgroundWindow.prototype.registerDialog = function(window) {};
+
+/**
+ * @param {Object=} opt_appState App state.
+ * @param {number=} opt_id Window id.
+ * @param {LaunchType=} opt_type Launch type. Default: ALWAYS_CREATE.
+ * @param {function(string)=} opt_callback Completion callback with the App ID.
+ */
+BackgroundWindow.prototype.launchFileManager =
+    function(opt_appState, opt_id, opt_type, opt_callback) {};