Roll src/third_party/skia/ 60c05f98a..7a1cc6766 (4 commits).

https://skia.googlesource.com/skia.git/+log/60c05f98aa22..7a1cc6766d07

$ git log 60c05f98a..7a1cc6766 --date=short --no-merges --format='%ad %ae %s'
2016-12-14 msarett SkPngCodec: Add support for 16-bit pngs (step 1)
2016-12-14 caryclark more simplify bugs
2016-12-14 brianosman Move, rename, and document Visual Studio GN helper script
2016-12-14 msarett Prefer F16 in SkAndroidCodec for high precision images

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/2575903002
Cr-Commit-Position: refs/heads/master@{#438570}

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': '60c05f98aa22d89e4ef25acb4799936f5df3cff2',
+  'skia_revision': '7a1cc6766d07f343923587deaf14e1a3965c2b8f',
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling V8
   # and whatever else without interference from each other.