Remove SkPaint dirty bits.

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:

Committed: https://skia.googlesource.com/skia/+/610a015fda84cd5d1e3f3f826bab393f1193bc0e

[mtklein, 2014-09-25 18:05:51]

mtklein@google.com changed reviewers:
+ mtklein@google.com, reed@google.com

[reed1, 2014-09-25 18:36:21]

The diff is nearly all RED -- (i.e. deletions)

lgtm

[mtklein, 2014-09-25 18:47:27]

The CQ bit was checked by mtklein@google.com

[commit-bot: I haz the power, 2014-09-25 18:48:17]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/604813003/1

[commit-bot: I haz the power, 2014-09-25 18:52:32]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2014-09-25 18:52:33]

Try jobs failed on following builders:
  Build-Win-VS2013-x86-Debug-Trybot on tryserver.skia
(http://108.170.220.76:10117/builders/Build-Win-VS2013-x86-Debug-Trybot/builds...)

[mtklein, 2014-09-25 18:56:48]

The CQ bit was checked by mtklein@google.com

[commit-bot: I haz the power, 2014-09-25 18:57:45]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/604813003/1

[commit-bot: I haz the power, 2014-09-25 18:57:57]

Committed patchset #1 (id:1) as 610a015fda84cd5d1e3f3f826bab393f1193bc0e