Roll src/third_party/skia/ ab00f4222..615af784a (2 commits).

https://chromium.googlesource.com/skia.git/+log/ab00f4222c9f..615af784ab6e

$ git log ab00f4222..615af784a --date=short --no-merges --format='%ad %ae %s'
2016-09-15 djsollen Revert of Update version of SVG asset (patchset #1 id:1 of https://codereview.chromium.org/2341043003/ )
2016-09-15 mtklein GN: support 32-bit x86 builds

CQ_INCLUDE_TRYBOTS=master.tryserver.blink:linux_precise_blink_rel
TBR=djsollen@google.com

Review-Url: https://codereview.chromium.org/2344893004
Cr-Commit-Position: refs/heads/master@{#418972}

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': 'ab00f4222c9fff8c08873e1218e79f49845f95a1',
+  'skia_revision': '615af784ab6ee0a1394b0ce62a49fce7be157451',
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling V8
   # and whatever else without interference from each other.