Allows tab dragging when maximized on aura. To fix it I made it so

ash/wm/window_util.h

Index: ash/wm/window_util.h
diff --git a/ash/wm/window_util.h b/ash/wm/window_util.h
index 1742cf732ec7a4257f9f03ea5d9c3c8ac119799c..4d7b3d619a2308a339224c93f801466a378a060f 100644
--- a/ash/wm/window_util.h
+++ b/ash/wm/window_util.h
@@ -30,6 +30,9 @@ ASH_EXPORT aura::Window* GetActiveWindow();
 // this is probably what you're looking for.
 ASH_EXPORT aura::Window* GetActivatableWindow(aura::Window* window);
 
+// Returns true if |window| is normal or default.
+ASH_EXPORT bool IsWindowNormal(aura::Window* window);
+
 // Returns true if |window| is in the maximized state.
 ASH_EXPORT bool IsWindowMaximized(aura::Window* window);