use addTab instead of loadOneTab (fixes #740) (#753)

Author: sam113101

common/content/liberator.js

@@ -838,8 +838,9 @@ const Liberator = Module("liberator", {
                     }
 
                     options.withContext(function () {
-                        options.setPref("browser.tabs.loadInBackground", true);
-                        browser.loadOneTab(url, null, null, postdata, where == liberator.NEW_BACKGROUND_TAB);
+                        browser.addTab(url, { postData: postdata });
+                        if (where != liberator.NEW_BACKGROUND_TAB)
+                            browser.selectTabAtIndex(-1);
                     });
                     break;