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

ash/wm/workspace/workspace_layout_manager.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_WORKSPACE_WORKSPACE_LAYOUT_MANAGER_H_
 #define ASH_WM_WORKSPACE_WORKSPACE_LAYOUT_MANAGER_H_
 #pragma once
 
 #include "ash/ash_export.h"
 #include "base/basictypes.h"
 #include "base/compiler_specific.h"
 #include "ui/aura/layout_manager.h"
+#include "ui/aura/window_observer.h"
 
 namespace aura {
 class MouseEvent;
 class Window;
 }
 
 namespace gfx {
 class Rect;
 }
 
 namespace ash {
 namespace internal {
 
 class WorkspaceManager;
 
 // LayoutManager for top level windows when WorkspaceManager is enabled.
-class ASH_EXPORT WorkspaceLayoutManager : public aura::LayoutManager {
+class ASH_EXPORT WorkspaceLayoutManager : public aura::LayoutManager,
+                                          public aura::WindowObserver {
  public:
   explicit WorkspaceLayoutManager(WorkspaceManager* workspace_manager);
   virtual ~WorkspaceLayoutManager();
 
   // Returns the workspace manager for this container.
   WorkspaceManager* workspace_manager() {
     return workspace_manager_;
   }
 
   // Overridden from aura::LayoutManager:
   virtual void OnWindowResized() OVERRIDE;
   virtual void OnWindowAddedToLayout(aura::Window* child) OVERRIDE;
   virtual void OnWillRemoveWindowFromLayout(aura::Window* child) OVERRIDE;
   virtual void OnChildWindowVisibilityChanged(aura::Window* child,
                                               bool visibile) OVERRIDE;
   virtual void SetChildBounds(aura::Window* child,
                               const gfx::Rect& requested_bounds) OVERRIDE;
 
+  // Overriden from aura::WindowObserver:
+  virtual void OnWindowPropertyChanged(aura::Window* window,
+                                       const void* key,
+                                       intptr_t old) OVERRIDE;
+
  private:
   // Owned by WorkspaceController.
   WorkspaceManager* workspace_manager_;
 
   DISALLOW_COPY_AND_ASSIGN(WorkspaceLayoutManager);
 };
 
 }  // namespace internal
 }  // namespace ash
 
 #endif  // ASH_WM_WORKSPACE_WORKSPACE_LAYOUT_MANAGER_H_