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

ash/wm/workspace_controller.cc

 // 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.
 
 #include "ash/wm/workspace_controller.h"
 
 #include "ash/shell.h"
 #include "ash/wm/window_util.h"
 #include "ash/wm/workspace/workspace_event_filter.h"
 #include "ash/wm/workspace/workspace_layout_manager.h"
@@ skipping 27 matching lines @@
   viewport->SetLayoutManager(layout_manager_);
   Shell::GetRootWindow()->AddRootWindowObserver(this);
   Shell::GetRootWindow()->AddObserver(this);
   workspace_manager_->set_grid_size(kGridSize);
   event_filter_->set_grid_size(kGridSize);
 }
 
 WorkspaceController::~WorkspaceController() {
   Shell::GetRootWindow()->RemoveObserver(this);
   Shell::GetRootWindow()->RemoveRootWindowObserver(this);
+  // WorkspaceLayoutManager may attempt to access state from us. Destroy it now.
+  if (viewport_->layout_manager() == layout_manager_)
+    viewport_->SetLayoutManager(NULL);
 }
 
 void WorkspaceController::ToggleOverview() {
   workspace_manager_->SetOverview(!workspace_manager_->is_overview());
 }
 
 void WorkspaceController::ShowMenu(views::Widget* widget,
                                    const gfx::Point& location) {
 #if !defined(OS_MACOSX)
   ui::SimpleMenuModel menu_model(this);
@@ skipping 58 matching lines @@
 }
 
 bool WorkspaceController::GetAcceleratorForCommandId(
       int command_id,
       ui::Accelerator* accelerator) {
   return false;
 }
 
 }  // namespace internal
 }  // namespace ash