mash: wires up shadows for mash

ui/wm/core/shadow.cc

Index: ui/wm/core/shadow.cc
diff --git a/ui/wm/core/shadow.cc b/ui/wm/core/shadow.cc
index 9a4b81c6356b2b8b9a7b9915d57e4eef468c00d2..2d7d0d44e3fb7405fcd8f14385d2fad8158ebb1b 100644
--- a/ui/wm/core/shadow.cc
+++ b/ui/wm/core/shadow.cc
@@ -32,6 +32,7 @@ Shadow::Shadow()
 Shadow::~Shadow() {}
 
 void Shadow::Init(ShadowElevation elevation) {
+  DCHECK_NE(ShadowElevation::DEFAULT, elevation);
   desired_elevation_ = elevation;
   layer_.reset(new ui::Layer(ui::LAYER_NOT_DRAWN));
   RecreateShadowLayer();
@@ -48,6 +49,7 @@ void Shadow::SetContentBounds(const gfx::Rect& content_bounds) {
 }
 
 void Shadow::SetElevation(ShadowElevation elevation) {
+  DCHECK_NE(ShadowElevation::DEFAULT, elevation);
   if (desired_elevation_ == elevation)
     return;