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

ash/wm/workspace_controller.cc

Index: ash/wm/workspace_controller.cc
diff --git a/ash/wm/workspace_controller.cc b/ash/wm/workspace_controller.cc
index 77868fc0dfb61c06f9755314ddf15e48e88183f3..f23fcc9d999ab90d706b9e3cf75a48d9f44e104a 100644
--- a/ash/wm/workspace_controller.cc
+++ b/ash/wm/workspace_controller.cc
@@ -45,6 +45,9 @@ WorkspaceController::WorkspaceController(aura::Window* viewport)
 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() {