I agree that onLoadFInished is supposed to follow onLoadStarted, so this is generally useless.

However, if one of our assumptions about the initial session state is incorrect, then this could happen. Since it is fairly bad for us to call a callback twice, I thought it was helpful to add this line also.

For example, if the page is already loading a frame in the background when execFuncAndWaitForLoadDecorator starts, then the background frame load could trigger onLoadFinished before our target function triggers onLoadStarted. This is what happened to me - so that bug is fixed now, but it raised the issue of whether we should be more defensive.