Directive Injector incorrectly computes direct childe visibility

[mhevery]

imagine you have tabs and pane directives where pane has to be a direct child of tabs

<tabs>
  <pane title="Overview"> foo text </pane>
</tabs>

The above works, but so does this:

<tabs>
  <div>
    <pane title="Overview"> foo text </pane>
  </div>
</tabs>

but it should not. It works because div has no associated injector and so pane thinks it is a child of tabs

the strange part is that by adding a directive to div it will create a new injector and break the direct parent/child relationship between tabs and pane