Roll src/third_party/skia/ 81681949d..901257a3b (15 commits).

https://chromium.googlesource.com/skia.git/+log/81681949d363..901257a3ba1d

$ git log 81681949d..901257a3b --date=short --no-merges --format='%ad %ae %s'
2016-07-21 mtklein GN: remove hooks again
2016-07-21 mtklein No symlink.  The bots are not running hooks anyway.
2016-07-21 bungeman Fix SkScalerContext_FreeType::generateFontMetrics.
2016-07-21 brianosman Add SkColorSpace to GrDrawContext
2016-07-21 herb In the current code, tiling and bilerp sampling are strongly tied together. They can be separated by taking advantage of observation that translating a sample point into filter points in the bilerp stage the filter points will be at most 0.5 outside the tile. This allows simplified repositioning for the various tiling modes; clamp and mirror use min and max while repeat has max -> 0 and 0-> max. This allows bilerp to simply treat the filter points that fall off the tile. This allows tiling and bilerp sampling to be totally separate.
2016-07-21 msarett Miscellaneous color space refactors
2016-07-21 mtklein GN: add missing .exe
2016-07-21 bsalomon Reenable support for CHROMIUM_set_uniform_location
2016-07-21 caryclark let line/cubic intersect at four spots
2016-07-21 mtklein Basic standalone GN configs.
2016-07-21 dvonbeck Fixed GM:lightingshader2 size
2016-07-21 robertphillips Retract PipelineBuilder some more
2016-07-21 msarett Drop support for libjpeg-turbo < 1.2 in SkJpegCodec
2016-07-21 msarett Remove unnecessary getColorSpace() API from SkCodec
2016-07-21 egdaniel Setup system in Vulkan to reuse VkDescriptorSet allocations.

CQ_INCLUDE_TRYBOTS=master.tryserver.blink:linux_blink_rel
TBR=jcgregorio@google.com

Review-Url: https://codereview.chromium.org/2167973005
Cr-Commit-Position: refs/heads/master@{#407018}

DEPS

@@ -36,7 +36,7 @@ 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': '81681949d363f777809af167c70912ca2a612036',
+  'skia_revision': '901257a3ba1d094280b4e1e0868bc0bcd137145a',
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling V8
   # and whatever else without interference from each other.