Remove support for SkPicture::clone().

Remove support for SkPicture::clone().

This folds SK_SUPPORT_LEGACY_PICTURE_CLONE through as undefined.

Chrome's not used clone() for a month or two, and we don't use it ourselves.
Don't think Android ever did.

CQ_EXTRA_TRYBOTS=tryserver.skia:Canary-Chrome-Ubuntu13.10-Ninja-x86_64-ToT-Trybot

BUG=skia:

Committed: https://skia.googlesource.com/skia/+/5bc760a6a6a61ff462a204e0c051ad6147760223

[mtklein, 2014-09-30 17:01:34]

The CQ bit was checked by mtklein@google.com

[commit-bot: I haz the power, 2014-09-30 17:02:06]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/620533002/1

[commit-bot: I haz the power, 2014-09-30 17:02:07]

Note for Reviewers:
The CQ is waiting for an approval.
If you believe that the CL is not ready yet, or if you would like to L-G-T-M
with comments then please uncheck the CQ checkbox.

Waiting for LGTM from a valid reviewer till 2014-09-30 23:02 UTC

[commit-bot: I haz the power, 2014-09-30 17:02:13]

Presubmit check for 620533002-1 failed and returned exit status 1.

Running presubmit commit checks ...

** Presubmit ERRORS **
Since the CL is editing public API, you must have an LGTM from one of:
('reed@chromium.org', 'reed@google.com', 'bsalomon@chromium.org',
'bsalomon@google.com', 'djsollen@chromium.org', 'djsollen@google.com')

[mtklein, 2014-09-30 17:03:01]

The CQ bit was checked by mtklein@google.com

[commit-bot: I haz the power, 2014-09-30 17:03:06]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/620533002/20001

[mtklein, 2014-09-30 17:06:56]

The CQ bit was unchecked by mtklein@google.com

[mtklein, 2014-09-30 17:07:37]

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

[mtklein, 2014-09-30 17:07:38]

This one needs an include/ stamp.  All deletions!

[robertphillips, 2014-09-30 17:11:19]

robertphillips@google.com changed reviewers:
+ robertphillips@google.com

[robertphillips, 2014-09-30 17:11:19]

lgtm

[reed1, 2014-09-30 17:12:42]

api lgtm

[mtklein, 2014-09-30 17:14:03]

The CQ bit was checked by mtklein@google.com

[commit-bot: I haz the power, 2014-09-30 17:14:16]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/620533002/20001

[commit-bot: I haz the power, 2014-09-30 18:14:44]

Committed patchset #2 (id:20001) as 5bc760a6a6a61ff462a204e0c051ad6147760223