This test checks that if style sheet is removed between two inspector launches it is not reported to frontend.

Running test
Opening front-end for the first time
Enabling CSS domain.
 - style sheet added: foo.css
 - style sheet added: bar.css
Closing inspector.

Removing style sheet.

Reopening inspector.
Running test
Opening front-end second time
Enabling CSS domain.
 - style sheet added: bar.css