Roll src/third_party/skia/ 4993b95f5..291c62a0f (7 commits).

https://skia.googlesource.com/skia.git/+log/4993b95f532f..291c62a0ff2c

$ git log 4993b95f5..291c62a0f --date=short --no-merges --format='%ad %ae %s'
2016-12-09 halcanary clean up old Makefiles
2016-12-09 jcgregorio docs: Use the new floating ment on skpaint.md
2016-12-09 halcanary SkImageEncoder::* going away
2016-12-08 fmalita [SVGDom] Clipped clipPath support
2016-12-09 mtklein update Win/Android toolchain setup after rolling GN
2016-12-09 djsollen Don't compile the Skia tools for PDK builds.
2016-12-09 halcanary Commit Queue: Add NoGPU build bot.

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=herb@google.com

Review-Url: https://codereview.chromium.org/2554423006
Cr-Commit-Position: refs/heads/master@{#437592}

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': '4993b95f532fdfc1996809189aa7e24ee839d983',
+  'skia_revision': '291c62a0ff2ca8a98cb30fcdaa6587f8a61bed98',
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling V8
   # and whatever else without interference from each other.