Validate incoming window properties.

ui/wm/core/shadow_types.cc

Index: ui/wm/core/shadow_types.cc
diff --git a/ui/wm/core/shadow_types.cc b/ui/wm/core/shadow_types.cc
index bf08bbec57e5b72081f292049f2ed898906fac4c..4f3e6f9a975bac8d040a43ff358aa664ed43f1d1 100644
--- a/ui/wm/core/shadow_types.cc
+++ b/ui/wm/core/shadow_types.cc
@@ -18,4 +18,12 @@ void SetShadowElevation(aura::Window* window, ShadowElevation elevation) {
   window->SetProperty(kShadowElevationKey, elevation);
 }
 
+bool IsValidShadowElevation(int64_t i) {
+  return i == int64_t(ShadowElevation::DEFAULT) ||
+         i == int64_t(ShadowElevation::NONE) ||
+         i == int64_t(ShadowElevation::SMALL) ||
+         i == int64_t(ShadowElevation::MEDIUM) ||
+         i == int64_t(ShadowElevation::LARGE);
+}
+
 }  // namespace wm