Generate path names on the client side

Pre-allocates a range of path names and manages allocations within
that range on the client side. This allows us to generate new path
objects in a feed-forward manner that doesn't require round trips to
the GL server.

BUG=skia:
R=bsalomon@google.com, markkilgard@gmail.com

Author: cdalton@nvidia.com

Review URL: https://codereview.chromium.org/304403003
9 files changed