[Dialog] Closed on browser back button

[sijithc40]

Bug, feature request, or proposal:

Dialog box is getting close while click on the browser back button, Can we avoid this?

What is the expected behavior?

Popup should not be close while clicking on the browser backbutton

What is the current behavior?

I want to do some functionality in the elements inside the popup while clicking on the browser back button. Now the popup is getting close.

What are the steps to reproduce?

Providing a StackBlitz/Plunker (or similar) is the best way to get the team to see your issue.

Plunker starter (using on @master): https://goo.gl/uDmqyY

StackBlitz starter (using latest npm release): https://goo.gl/wwnhMV

What is the use-case or motivation for changing an existing behavior?

Which versions of Angular, Material, OS, TypeScript, browsers are affected?

Is there anything else we should know?