chromium: Correct tools path in blink_idl_parser.

This is because of our symlink mess, as Chromium's build support scripts
are trying to resolve everything based on absolute paths and we split
off the bundled sources from the main derivation.

Yes, I'm refering to this as a mess, because in the end, we're going to
patch up the gyp files and use references someday.

Signed-off-by: aszlig <aszlig@redmoonstudios.org>