Remove SkPaint dirty bits.

fDirtyBits is only used by SkPaint::FlatteningTraits, which in turn was
only used as a smaller, faster format to flatten paints in-memory to dedup
them in the old picture backend.

SkRecord obsoleted all this.  Neither flatten()/unflatten() (disk format)
nor FlatteningTraits is used anywhere performance or size matters.

Here I revert the deduping code back to using the disk format for flattened paints.
We stil do have to flatten and unflatten paints while coverting from SkRecord
backend to the old backend, so we can't just delete this all yet, but any
faithful round trip flatten()/unflatten() pair will be fine, however slow.

NOTRY=true

BUG=skia:
R=reed@google.com, mtklein@google.com

Author: mtklein@chromium.org

Review URL: https://codereview.chromium.org/604813003
5 files changed