reland of https://codereview.chromium.org/11364053/ w/o removing the per-rootwindow stacking client

ui/views/widget/native_widget_aura.cc

Index: ui/views/widget/native_widget_aura.cc
diff --git a/ui/views/widget/native_widget_aura.cc b/ui/views/widget/native_widget_aura.cc
index 4e47ab20ac5e6f69bdb7307f7651cc1e89811087..46a9d2b3068492cde527052cb78c99c6bc5d1826 100644
--- a/ui/views/widget/native_widget_aura.cc
+++ b/ui/views/widget/native_widget_aura.cc
@@ -124,7 +124,7 @@ void NativeWidgetAura::InitNativeWidget(const Widget::InitParams& params) {
     // the |window_| using the desired |window_bounds|.
     if (!parent) {
       parent = aura::client::GetStackingClient(params.GetParent())->
-          GetDefaultParent(window_, window_bounds);
+          GetDefaultParent(params.context, window_, window_bounds);
     } else if (window_bounds == gfx::Rect()) {
       // If a parent is specified but no bounds are given,
       // use the origin of the parent's display so that the widget