Both PRenderFrame() and InitRenderFrame() are sync messages from child to parent and based on profiles we end up waiting for the reply from the parent. So,if we could do just one wait, not two. It is hard to estimate how much that would help, but we end up waiting for >10ms waiting for the replies.

Ah, this is a recent regression, from bug 919878

I guess it would be fine to merge them as long as we keep the success parameter. I think I split them up because it seemed weird to have the constructor behave that way. But if it matters for performance, it seems fine.

It seems to be rather important from performance point of view. Child process is just waiting for quite some time doing nothing. (But need to think about initialization steps a bit more. I think we should aim for no sync child-parent messages during normal <iframe mozbrowser> initialization.)

Commit message: "Bug 1003041 - Merge PRenderFrame() and InitRenderFrame() to avoid extra sync child->parent messaging, r=billm"