Roll src/third_party/skia/ 291c62a0f..e29ce641d (4 commits).

https://skia.googlesource.com/skia.git/+log/291c62a0ff2c..e29ce641d378

$ git log 291c62a0f..e29ce641d --date=short --no-merges --format='%ad %ae %s'
2016-12-09 kjlubick Move 6p arm64 CPU tests to Pixel C
2016-12-09 brianosman Make command buffer sRGB mip-mapping more predictable
2016-12-09 herb Revert "SkImageEncoder::* going away"
2016-12-09 mtklein Run bin/fetch-gn as a gclient hook.

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/2564893003
Cr-Commit-Position: refs/heads/master@{#437636}

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': '291c62a0ff2ca8a98cb30fcdaa6587f8a61bed98',
+  'skia_revision': 'e29ce641d378022a18f1dac731a71784b3eb5a11',
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling V8
   # and whatever else without interference from each other.