[gnome-shell] Improve notification documentation

[Florian Müllner <fmuellner src gnome org>]

commit fdaddbd1e050016850c0c1e2998be63d67ad622a
Author: Ole Jørgen Brønner <olejorgenb yahoo no>
Date:   Mon May 21 21:07:09 2018 +0200

    Improve notification documentation
    
    Ref: https://gitlab.gnome.org/GNOME/gnome-shell/issues/294

 js/ui/messageList.js |  1 +
 js/ui/messageTray.js | 10 ++++++----
 2 files changed, 7 insertions(+), 4 deletions(-)
---
diff --git a/js/ui/messageList.js b/js/ui/messageList.js
index aff201ed6..6ba5be858 100644
--- a/js/ui/messageList.js
+++ b/js/ui/messageList.js
@@ -27,6 +27,7 @@ function _fixMarkup(text, allowMarkup) {
 
         // Support <b>, <i>, and <u>, escape anything else
         // so it displays as raw markup.
+        // Ref: https://developer.gnome.org/notification-spec/#markup
         _text = _text.replace(/<(?!\/?[biu]>)/g, '&lt;');
 
         try {
diff --git a/js/ui/messageTray.js b/js/ui/messageTray.js
index 9ce5b4460..463d40ecf 100644
--- a/js/ui/messageTray.js
+++ b/js/ui/messageTray.js
@@ -315,10 +315,10 @@ var NotificationApplicationPolicy = new Lang.Class({
 // You can add a secondary icon to the banner with 'secondaryGIcon'. There
 // is no fallback for this icon.
 //
-// If @params contains 'bannerMarkup', with the value %true, then
-// the corresponding element is assumed to use pango markup. If the
-// parameter is not present for an element, then anything that looks
-// like markup in that element will appear literally in the output.
+// If @params contains 'bannerMarkup', with the value %true, a subset (<b>,
+// <i> and <u>) of the markup in [1] will be interpreted within @banner. If
+// the parameter is not present, then anything that looks like markup
+// in @banner will appear literally in the output.
 //
 // If @params contains a 'clear' parameter with the value %true, then
 // the content and the action area of the notification will be cleared.
@@ -328,6 +328,8 @@ var NotificationApplicationPolicy = new Lang.Class({
 // If @params contains 'soundName' or 'soundFile', the corresponding
 // event sound is played when the notification is shown (if the policy for
 // @source allows playing sounds).
+//
+// [1] https://developer.gnome.org/notification-spec/#markup 
 var Notification = new Lang.Class({
     Name: 'Notification',