mash: wires up shadows for mash

services/ui/public/interfaces/window_manager.mojom

Index: services/ui/public/interfaces/window_manager.mojom
diff --git a/services/ui/public/interfaces/window_manager.mojom b/services/ui/public/interfaces/window_manager.mojom
index 2e8b5de976d04d295e0d571c226259e7c5b2f749..e3238d1822ca5887644c61197f0c6c0372e3a4aa 100644
--- a/services/ui/public/interfaces/window_manager.mojom
+++ b/services/ui/public/interfaces/window_manager.mojom
@@ -121,6 +121,9 @@ interface WindowManager {
   // Type: gfx::Rect.
   const string kRestoreBounds_Property = "prop:restore-bounds";
 
+  // See ShadowElevation for details. Type: wm::ShadowElevation.
+  const string kShadowElevation_Property = "prop:shadow-elevation";
+
   // The type of item to be shown on the shelf for this window. Type: int
   // A few ash::ShelfItemType values are supported; TYPE_UNKNOWN means no item.
   const string kShelfItemType_Property = "prop:shelf-item-type";