Browser instance created through script doesn't cycle with ALT+TAB

I am using a bash file with a line chromium-browser http://www.gmail.com to create a browser instance. This browser instance doesn't cycle with ALT+TAB. How to fix this?

Sometimes it does. And in this case the code below doesn't get executed. I noticed that the arrow to the browser instance on the sidebar looks different in two cases. So I am attaching screen shots:

• The one with the solid arrow, which is on the left cycles. But the code below it doesn't get executed. The subsequent lines get executed only after I close this browser instance.
• The one with a hollow arrow, which is on the right doesn't cycle.