Repeatable selser changes for parserTests.

We use the seedable random-number generator from the alea package
(npm install after you pull this commit).

The random number generator is seeded with the test case title, so
that the changes generated are repeatable, even if tests are rearranged
or new tests added.

Change-Id: If7eaf44d55a77d985afc0ee94b7e7eaa97b3ce6b
Merge "Repeatable selser changes for parserTests."