Several fixes for the next branch

Kudos to @ds-hwang for helping me debug the rendering issue which turned out to be a deadlock on the renderer process because of a sync message not being replied by browser process because the ExtensionServer was not created because a virtual method in the base class was renamed in the Content API. A lot of "becauses"! :suspect: 

All the utests and browsertests are passing on Linux (at least on my desktop).