[gnome-shell] Background: add a comment for questionable GSettings usage

[Giovanni Campagna <gcampagna src gnome org>]

commit 0068098996ed3ca443060800fb3d754421186cdb
Author: Giovanni Campagna <gcampagna gnome org>
Date:   Fri Mar 20 12:39:01 2015 -0700

    Background: add a comment for questionable GSettings usage
    
    BackgroundSource relies on Background to watch its own settings.
    Add a comment to explain that.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=746509

 js/ui/background.js |    4 ++++
 1 files changed, 4 insertions(+), 0 deletions(-)
---
diff --git a/js/ui/background.js b/js/ui/background.js
index 82928e7..5acff9f 100644
--- a/js/ui/background.js
+++ b/js/ui/background.js
@@ -527,6 +527,10 @@ const BackgroundSource = new Lang.Class({
         let file = null;
         let style;
 
+        // We don't watch changes to settings here,
+        // instead we rely on Background to watch those
+        // and emit 'changed' at the right time
+
         if (this._overrideImage != null) {
             file = Gio.File.new_for_path(this._overrideImage);
             style = GDesktopEnums.BackgroundStyle.ZOOM; // Hardcode