We already have full access to all sites via our content script so this permission doesn't add anything new but we need it to be able to establish page connection via tabs.executeScript when the extension is installed, reloaded, re-enabled.
<all_urls> also allows file:// URLs unlike *://*/* used previously. Of course it requires the corresponding checkbox being enabled on chrome://extensions page.
chrome://favicon doesn't indicate an icon is missing in any way, it simply shows a placeholder instead. It also doesn't extrapolate from sub-pages so `example.com` won't have a favicon even if `example.com/subpage` has one.
* documentElement may be overwritten right after iframe was initialized with contentDocument.write() and due to this change being external it's not reported in our existing rewrite observer so we enqueue an additional check using setTimeout(0).
* match_about_blank in manifest.json is back
* iframes with src = about: or javascript: don't have a proper URL when our content script runs so we get the real URL from the parent window
* minor refactoring
To prevent cross-page leaks we need to create/copy prefs and cachedStyles inside the background page context.
* storage.js is now used only in the background page
* messaging.js now contains less bg-specific methods and more common methods. Added saveStyleSafe, deleteStyleSafe which automatically invoke onRuntimeMessage of the current page or just handleUpdate/handleDelete when notify:false
* prefs.js with 'prefs' for background and UI pages: separate objects because a UI page may load before the background page and it can read prefs from localStorage/sync/defaults
* hotkey to open Manage styles
* hotkey to enable/disable all styles
No default hotkeys are provided, to customize go to "Keyboard shortcuts" on the Extensions page
