Awesome work!

Possible enhancements:
* Bookmarks in krunner
* After a short notification sound has played during a longer video, the media control plasmoid is stuck on that (paused) notification sound.
* Everytime the browser is opened, a new tab is opened and closed very quickly. After that, always the rightmost tab is focused.
* Maybe also unrelated: XML files don't display correctly (maybe due to your content script)

For everyone wondering how to install: The corresponding host application plasma-browser-integration is available in the Neon Unstable repository (http://archive.neon.kde.org/dev/unstable/pool/main/p/plasma-browser-integration/)