Dead code in maybe_serialize function

[jacobsantos]

Looking at the code of maybe_serialize() caused some confusion, because it doesn't appear that the code will ever execute as the first if branch will always evaluate serialized data to be true. This means that when the execution gets down to

    if ( is_serialized( $data ) )   // <--- Always false
        return serialize( $data );  // <--- Dead Code

This probably needs to be moved up a bit to the top of the function body.

Test cases for maybe_serialize()

The test cases need to be patched in the wp-testcases folder in the Automattic WordPress Tests repository.

There has been a previous discussion on the topic in #4029 and I suppose the expected result is that serialized data should be serialized again.

Duplicate of #7347.