Althought the construction of the XML document was fine witn Android 7,
the actual serialization of it was limited to 8 or higher. Try as I might,
I couldn't find a way to figure out how to serialize a DOM tree on API 7.
Turns out that the "PullParser" API is able to build and serialize XML
trees on API 7. It's a little clunkier than the DOM alternative, so I
refactored out the generation into a subclass to make it clearer what
it is doing and when.
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