Always active Window (Always Visible) by Brian

This extension protects against web pages tracking the activity state of the page. Some websites use this track to only offer services when the tab is active. By installing this extension a small script is injected into every webpage which overwrites the "document.visibilityState", and "document.hidden" properties to pretend the tab is always in the active state (document.visibilityState = 'visible' and document.hidden = false).

This is useful for the webpages that check your visibility state before loading resources like many music webpages. By installing this extension even if the page is opened in the background page, the player will start immediately like the page is loaded on an active tab.

Supported Trackings:
document.mozHidden (only on Firefox browser)
document.webkitHidden (only on Chromium browsers)

Supported Events:
1. visibilitychange
2. webkitvisibilitychange (only on Chromium browsers)
3. mozvisibilitychange (only on Firefox browser)
4. blur (some websites require the user to keep the tab focused)
5. mouseleave (some websites use this method to make sure the user pointer is inside the window)

Notes:
At the moment there is no exception list, so the extension injects the script on all HTTP and local HTML pages. You need to disable the extension from the options page if you need to bypass the default always active behavior. On Chromium browsers, you can also limit the script injection to a few hostnames by using the right-click context menu item called "This Can Read and Change Site Data" over the browser action button.