Comment 3 for bug 235267

I agree that seeing a error at 3 would be best.

Instead of popByName(), I think we want a slightly different behaviour from the current pop(). I think we want a restore(config_data_name), which makes the named ConfigData the top of the stack, the items that were above it are lost. This feature makes it easier to restore the config to a known state. There are two cases for this:

    1. A layer pushes a marker config onto the overlays so that it can be
        restored for the next test.
        layer -> config.push('pagetestlayer', '')
         test -> config.push('test data', test_data)
         test -> config.push('test data 2', test_data_2)
        layer -> config.restore('pagetestlayer')

    2. A test saves the name of the top config_data to restore it.
        starting_state = config.overlays[0].name
        ... lots of config.push() calls
        config.restore(starting_state)