Bug 899347 - [e10s] Make click-to-play work with e10s. Originally written by mbrubeck. r=gfritzsche,felipe,Unfocused.

We now use message passing and content scripts in order to implement click-to-play. This allows
us to use click-to-play in e10s windows.

--HG--
extra : rebase_source : 6239a4b49e0af89800c5618e4589f8aef03f58d4