explicitly track if a path is finite or not

explicitly track if a path is finite or not
we need this (it appears) so we can definitively reject non-finite paths
in canvas, before passing them down into the guts.
Committed: https://code.google.com/p/skia/source/detail?r=4784

[reed1, 2012-07-25 21:43:43]

will add unittests before final

[bsalomon, 2012-07-26 12:30:57]

On 2012/07/25 21:43:43, reed1 wrote:
> will add unittests before final

It LGTM (with tests).