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

ui/views/widget/widget.cc

Index: ui/views/widget/widget.cc
diff --git a/ui/views/widget/widget.cc b/ui/views/widget/widget.cc
index bdc355b5126f1e40fa9daa726a79090d10cfa154..adb3c6c873e5c203ca4c63be94c61af35eb776ed 100644
--- a/ui/views/widget/widget.cc
+++ b/ui/views/widget/widget.cc
@@ -159,7 +159,8 @@ Widget::InitParams::InitParams()
       native_widget(NULL),
       desktop_root_window_host(NULL),
       top_level(false),
-      layer_type(ui::LAYER_TEXTURED) {
+      layer_type(ui::LAYER_TEXTURED),
+      context(NULL) {
 }
 
 Widget::InitParams::InitParams(Type type)
@@ -184,7 +185,8 @@ Widget::InitParams::InitParams(Type type)
       native_widget(NULL),
       desktop_root_window_host(NULL),
       top_level(false),
-      layer_type(ui::LAYER_TEXTURED) {
+      layer_type(ui::LAYER_TEXTURED),
+      context(NULL) {
 }
 
 gfx::NativeView Widget::InitParams::GetParent() const {