Bug 1368194 - add tooltiptext to 'send to device' items in the page action menu, r=adw

MozReview-Commit-ID: JZDgR0d4puz

browser/base/content/browser.js

@@ -7864,6 +7864,7 @@ var gPageActionButton = {
       if (clientId) {
         item.classList.add("subviewbutton-iconic");
       }
+      item.setAttribute("tooltiptext", name);
       return item;
     });