Roll src/third_party/skia/ 7a1cc6766..e305cc1f2 (6 commits).

https://skia.googlesource.com/skia.git/+log/7a1cc6766d07..e305cc1f2a44

$ git log 7a1cc6766..e305cc1f2 --date=short --no-merges --format='%ad %ae %s'
2016-12-14 robertphillips Partially defer GrSWMaskHelper
2016-12-14 scroggo Remove SkKTXImageEncoder
2016-12-14 fmalita SK_API-export SkCodec
2016-12-08 scroggo Add SkCodec::FrameInfo::fFullyReceived
2016-12-14 reed remove PLAIN_ENUM flag for SkClipOp
2016-12-14 reed add tests/bench for dynamicwstream

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/2574323003
Cr-Commit-Position: refs/heads/master@{#438613}

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': '7a1cc6766d07f343923587deaf14e1a3965c2b8f',
+  'skia_revision': 'e305cc1f2a44e47d6a0dcc0ff34e2692349aed5d',
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling V8
   # and whatever else without interference from each other.