This is similar to the code we already have in JS tests, but instead
of printing to the console where you have to copy-paste from, it just
overwrites the files.
Also, update all of the expected results by this method.
Changes in the expected outputs:
* In JSON files, the "warnings" are now always in the same place
regardless of the type of the warning.
* In all HTML files, self-closing tags now include the trailing slash,
some characters are no longer encoded as entities when not necessary,
and attributes may be single-quoted when that makes them shorter.
* In Parsoid HTML files, the header is no longer terribly mangled.
Other notes:
* CommentParserTest.php: Change the output of serializeComments()
to be in similar order as in JS, to reduce the diffs in this commit
and because it's a better order for humans.
* modifier.test.js: Remove some hacks that were working around small
inconsistencies between the previous expected outputs and the actual
outputs.
Change-Id: I9f764640dae823321c0ac35898fa4db03f1ca364
