Code style cleanups to Sanitizer.php.

Fix warnings and errors from the PHP code style checker.

Note that phpcs is complaining about the constant '-1' -- it says:
'Expected 1 space after "-"; 0 found'.  That's ridiculous, so I didn't
"fix" that issue.

Change-Id: I87a50bbc5a4387ffbca9f55d07f66b6cf860a8ac
Merge "Code style cleanups to Sanitizer.php."