check if PP can work on current page on page' loading event.
1) check if url is "chrome://*"; 2) check if url is "file://*" and if access to file scheme is allowed
Merge branch 'feature/check-if-pp-can-work-on-current-page' of https://github.com/kroleg/perfectpixel into kroleg-feature/check-if-pp-can-work-on-current-page
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