Don't jump to top of page when returning from another tab.

This fixes Trac #723 - Message view scrolls to top after reloading on another tab (e.g. settings)

(imported from commit d9134cec6879625d577c43a08d258af3f6dacc5f)

zephyr/static/js/ui.js

@@ -638,9 +638,13 @@ $(function () {
         // because otherwise that action may scroll us somewhere.)
         if (scroll_positions.hasOwnProperty(target_tab)) {
             viewport.scrollTop(scroll_positions[target_tab]);
+        } else {
+            if (target_tab === '#home') {
+                scroll_to_selected();
             } else {
                 viewport.scrollTop(0);
             }
+        }
     });
 
     // N.B. that subs.setup_page calls focus() on our stream textbox,