Attempt 2: Allows tab dragging when maximized on aura. To fix it I made it so

ash/wm/window_util.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef ASH_WM_WINDOW_UTIL_H_
 #define ASH_WM_WINDOW_UTIL_H_
 #pragma once
 
 #include <set>
 
@@ skipping 12 matching lines @@
 ASH_EXPORT bool IsActiveWindow(aura::Window* window);
 ASH_EXPORT aura::Window* GetActiveWindow();
 
 // Retrieves the activatable window for |window|. If |window| is activatable,
 // this will just return it, otherwise it will climb the parent/transient parent
 // chain looking for a window that is activatable, per the ActivationController.
 // If you're looking for a function to get the activatable "top level" window,
 // 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);
 
 // Returns true if |window| is in the fullscreen state.
 ASH_EXPORT bool IsWindowFullscreen(aura::Window* window);
 
 // Maximizes |window|, which must not be NULL.
 ASH_EXPORT void MaximizeWindow(aura::Window* window);
 
 // Restores |window|, which must not be NULL.
 ASH_EXPORT void RestoreWindow(aura::Window* window);
 
 // Returns true if the set of |windows| contains a full-screen window.
 typedef std::set<aura::Window*> WindowSet;
 ASH_EXPORT bool HasFullscreenWindow(const WindowSet& windows);
 
 // Sets whether the window should be open in a split mode. Only applicable when
 // workspaces are used.
 ASH_EXPORT void SetOpenWindowSplit(aura::Window* window, bool value);
 ASH_EXPORT bool GetOpenWindowSplit(aura::Window* window);
 
 }  // namespace wm
 }  // namespace ash
 
 #endif  // ASH_WM_WINDOW_UTIL_H_