Tests that `Page.frameSubtreeWillBeDetached` event is emitted before the frame subtree is detached
... creating and navigating iframe http://127.0.0.1:8000/inspector-protocol/resources/same_origin_iframe.html
... iframe created and navigated
... removing the frame
Received event {
    method : Page.frameSubtreeWillBeDetached
    params : {
        frameId : <string 0>
    }
    sessionId : <string>
}
Received event {
    method : Page.frameDetached
    params : {
        frameId : <string 1>
        reason : remove
    }
    sessionId : <string>
}
Received event {
    method : Page.frameDetached
    params : {
        frameId : <string 0>
        reason : remove
    }
    sessionId : <string>
}
... done removing the frame
... creating and navigating iframe http://127.0.0.1:8000/inspector-protocol/resources/cross_origin_iframe.html
... iframe created and navigated
... removing the frame
Received event {
    method : Page.frameSubtreeWillBeDetached
    params : {
        frameId : <string 2>
    }
    sessionId : <string>
}
Received event {
    method : Page.frameDetached
    params : {
        frameId : <string 3>
        reason : remove
    }
    sessionId : <string>
}
Received event {
    method : Page.frameDetached
    params : {
        frameId : <string 2>
        reason : remove
    }
    sessionId : <string>
}
... done removing the frame
... creating and navigating iframe http://oopif.test:8000/inspector-protocol/resources/cross_origin_iframe.html
... iframe created and navigated
... removing the frame
Received event {
    method : Page.frameSubtreeWillBeDetached
    params : {
        frameId : <string 4>
    }
    sessionId : <string>
}
Received event {
    method : Page.frameDetached
    params : {
        frameId : <string 4>
        reason : remove
    }
    sessionId : <string>
}
... done removing the frame
... creating and navigating iframe http://devtools.test:8000/inspector-protocol/resources/cross_origin_iframe.html
... iframe created and navigated
... removing the frame
Received event {
    method : Page.frameSubtreeWillBeDetached
    params : {
        frameId : <string 5>
    }
    sessionId : <string>
}
Received event {
    method : Page.frameDetached
    params : {
        frameId : <string 6>
        reason : remove
    }
    sessionId : <string>
}
Received event {
    method : Page.frameDetached
    params : {
        frameId : <string 5>
        reason : remove
    }
    sessionId : <string>
}
... done removing the frame