BBHs: void* data -> unsigned data

Now that the old backend's not using BBHs, we can specialize them for
SkRecord's needs.  The only thing we really want to store is op index, which
should always be small enough to fit into an unsigned (unsigned also helps keep
it straight from other ints floating around).

This means we'll need half (32-bit) or a quarter (64-bit) the bytes in SkTileGrid,
because we don't have to store an extra int for ordering.

BUG=skia:2834

Review URL: https://codereview.chromium.org/617393004
14 files changed