aura: Draw drop shadows under browsers and menus.

ui/aura/aura_switches.cc

Index: ui/aura/aura_switches.cc
diff --git a/ui/aura/aura_switches.cc b/ui/aura/aura_switches.cc
index 2dd4ff39e48c26bb066759ca9e20ae3d61c07a7b..079e796b30fa6935aa851ca0654383791557c73b 100644
--- a/ui/aura/aura_switches.cc
+++ b/ui/aura/aura_switches.cc
@@ -8,6 +8,10 @@ namespace switches {
 
 // Initial dimensions for the host window in the form "1024x768".
 const char kAuraHostWindowSize[] = "aura-host-window-size";
+
+// Avoid drawing drop shadows under windows.
+const char kAuraNoShadows[] = "aura-no-shadows";
+
 // Use Aura-style window frames and drag behavior.
 const char kAuraWindows[] = "aura-windows";