Roll src/third_party/skia/ efa9d34cc..d1c550e71 (2 commits).

https://skia.googlesource.com/skia.git/+log/efa9d34ccbde..d1c550e71fa7

$ git log efa9d34cc..d1c550e71 --date=short --no-merges --format='%ad %ae %s'
2016-12-19 fmalita Consolidate TILEX_LOW_BITS/TILEY_LOW_BITS -> EXTRACT_LOW_BITS
2016-12-19 robertphillips "Fix" some ImageFilter fuzzer issues

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=rmistry@google.com

Review-Url: https://codereview.chromium.org/2587093002
Cr-Commit-Position: refs/heads/master@{#439517}

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': 'efa9d34ccbdeb541a1fa77a678552df7a08531be',
+  'skia_revision': 'd1c550e71fa72cfbf03b93c10ec8b9d1d109f8c2',
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling V8
   # and whatever else without interference from each other.