Added DCHECK to flag a potential memory leak.
Added DCHECK to flag a potential memory leak.

Calling Bind multiple times will leak internal_router_.

R=jamesr@chromium.org

Review URL: https://codereview.chromium.org/941273003

afandria/mojo,chinmaygarde/mojo,jianglu/mojo,chinmaygarde/mojo,jianglu/mojo,collinjackson/mojo,jianglu/mojo,collinjackson/mojo,afandria/mojo,collinjackson/mojo,collinjackson/mojo,jianglu/mojo,afandria/mojo,chinmaygarde/mojo,collinjackson/mojo,jianglu/mojo,chinmaygarde/mojo,jianglu/mojo,collinjackson/mojo,collinjackson/mojo,chinmaygarde/mojo,collinjackson/mojo,afandria/mojo,chinmaygarde/mojo,chinmaygarde/mojo,jianglu/mojo,afandria/mojo,chinmaygarde/mojo,collinjackson/mojo,afandria/mojo,jianglu/mojo,afandria/mojo,chinmaygarde/mojo,afandria/mojo