Roll src/third_party/skia/ 56ff9a1c9..c2ba75b50 (7 commits).

https://skia.googlesource.com/skia.git/+log/56ff9a1c9dfd..c2ba75b50750

$ git log 56ff9a1c9..c2ba75b50 --date=short --no-merges --format='%ad %ae %s'
2016-12-14 bungeman Remove Mac 10.6 - 10.8 work arounds for fonts.
2016-12-14 bungeman Remove strange 'write' overload on SkDynamicMemoryWStream.
2016-12-14 bsalomon Some more batch->op renaming
2016-12-14 msarett Reenable 16-bit png brd decode tests
2016-12-14 bsalomon Bring sk_sp to oval GrDrawOps and rename batch->op
2016-12-14 brianosman Make picture backed images sRGB by default
2016-12-14 robertphillips Demote savePixels to save_pixels

Documentation for the AutoRoller is here:
https://skia.googlesource.com/buildbot/+/master/autoroll/README.md

If the roll is causing failures, see:
http://www.chromium.org/developers/tree-sheriffs/sheriff-details-chromium#TOC-Failures-due-to-DEPS-rolls

CQ_INCLUDE_TRYBOTS=master.tryserver.blink:linux_trusty_blink_rel
TBR=msarett@google.com

Review-Url: https://codereview.chromium.org/2580623002
Cr-Commit-Position: refs/heads/master@{#438712}

DEPS

@@ -40,7 +40,7 @@ vars = {
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling Skia
   # and whatever else without interference from each other.
-  'skia_revision': '56ff9a1c9dfdaf1cd6db3b62a5c2b739cd242032',
+  'skia_revision': 'c2ba75b50750f2b200d98f100f0779da1c746565',
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling V8
   # and whatever else without interference from each other.