Let's move all this inside the class instead (make a new public method "Start()" or maybe "Launch"), 'StartExtensionProcess' should become private than. The client code should look like:
XWalkExtensionProcessLauncher::Launch(channel_id, client_fd);

or maybe we'd even better to expose C API, just a function "LaunchXWalkExtensionProcess()", I see that launcher now has started using C++ which wasn't the case before..