[gnome-shell/wip/fmuellner/es6-class-preparations: 17/18] messageTray: Split out policy creation

[Florian Müllner <fmuellner src gnome org>]

commit 8f15193b403fe7caa725096ef21ef88684b975f3
Author: Florian Müllner <fmuellner gnome org>
Date:   Wed Nov 1 19:21:31 2017 +0100

    messageTray: Split out policy creation
    
    The _createPolicy() method of a subclass usually depends on some
    constructor parameters that need to be set before chaining up to
    the parent. This works fine with Lang.Class, but will break with
    ES6 classes, as "this" is only initialized after chaining up.
    
    Prepare for this by not creating the policy in the constructor,
    but when it is first accessed.
    
    https://gitlab.gnome.org/GNOME/gnome-shell/merge_requests/350

 js/ui/messageTray.js | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)
---
diff --git a/js/ui/messageTray.js b/js/ui/messageTray.js
index fc4e00c9d..7ce977f47 100644
--- a/js/ui/messageTray.js
+++ b/js/ui/messageTray.js
@@ -701,7 +701,13 @@ var Source = new Lang.Class({
 
         this.notifications = [];
 
-        this.policy = this._createPolicy();
+        this._policy = null;
+    },
+
+    get policy() {
+        if (!this._policy)
+            this._policy = this._createPolicy();
+        return this._policy;
     },
 
     get count() {