Fix accessability for web notification tray.

ash/system/status_area_widget_delegate.cc

Index: ash/system/status_area_widget_delegate.cc
diff --git a/ash/system/status_area_widget_delegate.cc b/ash/system/status_area_widget_delegate.cc
index 0db7b0ada44fde2098ddc9f768125b8222a6a263..2c0e7d2766a6c0f7f561ff68611db9103c0a5041 100644
--- a/ash/system/status_area_widget_delegate.cc
+++ b/ash/system/status_area_widget_delegate.cc
@@ -96,14 +96,14 @@ void StatusAreaWidgetDelegate::UpdateLayout() {
                          views::GridLayout::USE_PREF, 0, 0);
     }
     layout->StartRow(0, 0);
-    for (int c = 0; c < child_count(); ++c)
+    for (int c = child_count() - 1; c >= 0; --c)
       layout->AddView(child_at(c));
   } else {
     columns->AddColumn(views::GridLayout::CENTER, views::GridLayout::CENTER,
                        0, /* resize percent */
                        views::GridLayout::USE_PREF, 0, 0);
-    for (int c = 0; c < child_count(); ++c) {
-      if (c != 0)
+    for (int c = child_count() - 1; c >= 0; --c) {
+      if (c != child_count() - 1)
         layout->AddPaddingRow(0, kTraySpacing);
       layout->StartRow(0, 0);
       layout->AddView(child_at(c));