int64 -> int64_t (etc) cleanup

A handful of places were using integer types without the _t suffix.
Fix 'em.

Review URL: https://codereview.chromium.org/644463004

git-svn-id: svn://svn.chromium.org/blink/trunk@184419 bbb929c8-8fbe-4397-9dbb-9b2b20218538