Add appIconMask to notification API

chrome/common/extensions/api/notifications.idl

Index: chrome/common/extensions/api/notifications.idl
diff --git a/chrome/common/extensions/api/notifications.idl b/chrome/common/extensions/api/notifications.idl
index da95e62c95a0c86116d435fe282fdccc2045521c..5f802fe2a728184200c986238813adefad249476 100644
--- a/chrome/common/extensions/api/notifications.idl
+++ b/chrome/common/extensions/api/notifications.idl
@@ -58,6 +58,12 @@ namespace notifications {
     DOMString? iconUrl;
     [nodoc] NotificationBitmap? iconBitmap;
 
+    // The alpha channel of app icon mask will be masked with white
+    // foreground and grey background, displayed on the bottom right corner
+    // of a notification

[not at google - send to devlin, 2014/07/15 15:17:54]

please phrase this comment in terms of the property, which is a noun. see
comments on all of these other properties as examples.

i'd also like to see what this URL actually is. a remote URL? a local URL? data
URL? same goes for all of the other comments on URL images (the iconUrls,
imageUrl). the comments of those could be better really; rather than "Sender's
avatar..." it should be "A URL to the sender's avatar...", with a second
paragraph "URLs can be ...".

and the comment should end with a period.

[liyanhou, 2014/07/21 16:51:34]

Done.

+    DOMString? appIconMaskUrl;
+    [nodoc] NotificationBitmap? appIconMaskBitmap;
+
     // Title of the notification (e.g. sender name for email).
     // <em>Required for $(ref:notifications.create)</em> method.
     DOMString? title;