Roll src/third_party/skia/ 53c02e015..6ef699901 (2 commits).

https://chromium.googlesource.com/skia.git/+log/53c02e015664..6ef6999017fe

$ git log 53c02e015..6ef699901 --date=short --no-merges --format='%ad %ae %s'
2016-09-14 mtklein GN: Android Vulkan support
2016-09-14 mtklein update derive_compile_bot_name() for GN_Android_Vulkan

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

Review-Url: https://codereview.chromium.org/2339183002
Cr-Commit-Position: refs/heads/master@{#418562}

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': '53c02e015664712649056b18b3d4da596b491186',
+  'skia_revision': '6ef6999017febaf0039b83c1ff4da1efe9c0e85d',
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling V8
   # and whatever else without interference from each other.