Bug 386163 - 'Set Desktop Background' refactoring: use canvas in all cases, support widescreen previews

p=Dao Gottwald <dao@design-noir.de>
r=mano, ui-r=mconnor

browser/themes/gnomestripe/browser/jar.mn

@@ -40,6 +40,7 @@ classic.jar:
         skin/classic/browser/Search-provider-mid-bottom.png
         skin/classic/browser/setDesktopBackground.css
         skin/classic/browser/monitor.png
+        skin/classic/browser/monitor_16-10.png
         skin/classic/browser/feeds/feedIcon.png                 (feeds/feedIcon.png)
         skin/classic/browser/feeds/feedIcon16.png               (feeds/feedIcon16.png)
         skin/classic/browser/feeds/subscribe.css                (feeds/subscribe.css)

browser/themes/gnomestripe/browser/setDesktopBackground.css

@@ -1,17 +1,14 @@
 @namespace url("http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul");
+@namespace html url("http://www.w3.org/1999/xhtml");
 
-#monitor {
+html|canvas#screen {
   margin: 12px 11px 32px;
-  width: 153px;
-  height: 114px;
-  overflow: hidden;
 }
 
-#monitorImage {
+#monitor {
   list-style-image: url("chrome://browser/skin/monitor.png");
 }
 
-#noPreviewAvailable {
-  background-color: white !important;
-  font-size: 12px !important;
+#monitor[aspectratio="16:10"] {
+  list-style-image: url("chrome://browser/skin/monitor_16-10.png");
 }