Roll src/third_party/skia/ 878df6dd0..29437eb5c (1 commit).

https://skia.googlesource.com/skia.git/+log/878df6dd03d1..29437eb5c782

$ git log 878df6dd0..29437eb5c --date=short --no-merges --format='%ad %ae %s'
2016-12-27 brianosman Add color space fallback for matrix convolution filter

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=liyuqian@google.com

Review-Url: https://codereview.chromium.org/2600953002
Cr-Commit-Position: refs/heads/master@{#440780}

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': '878df6dd03d1e5b8c018f803eff5b4736af399f8',
+  'skia_revision': '29437eb5c782ff49b9c2a23ef5dd4a54e9e45c44',
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling V8
   # and whatever else without interference from each other.