Uses vAPI to pass information from contentscript-start.js to contentscript-end.js

[gorhill]

A while ago I had concluded (after trying to make it work) content scripts lived in their own world, with their own global context. The vAPI from @Deathamns proves me wrong: all content scripts (for a same page or frame) share the same global context.

Looks like something else was going on at the time I checked, probably I was using a silly test case.

So this means the little "hack" I currently use to pass exception filters from contentscript-start to contentscript-end can be removed, and I will just use the vAPI object to pass the information, hence skipping the overhead of encoding/decoding the exceptions into a style tag attribute.

[gorhill]

Could remove more code/overhead than originally thought.

[gorhill]

Regression bug fixed with f141d6f. Test case: all hashtags where hidden in https://twitter.com