Roll src/third_party/skia 3c70f9acfc33..f7cf794890d4 (4 commits)

https://skia.googlesource.com/skia.git/+log/3c70f9acfc33..f7cf794890d4

git log 3c70f9acfc33..f7cf794890d4 --date=short --no-merges --format='%ad %ae %s'
2019-09-11 nifong@google.com Assert there are some sources when running skpbench
2019-09-11 kjlubick@google.com [canvaskit] expose ComputeTonalColors
2019-09-11 robertphillips@google.com Update comparison in BackendAllocation tests
2019-09-11 kjlubick@google.com [canvaskit] expose all 8 radii for RRect

Created with:
  gclient setdep -r src/third_party/skia@f7cf794890d4

If this roll has caused a breakage, revert this CL and stop the roller
using the controls here:
https://autoroll.skia.org/r/skia-autoroll
Please CC mtklein@google.com on the revert to ensure that a human
is aware of the problem.

To report a problem with the AutoRoller itself, please file a bug:
https://bugs.chromium.org/p/skia/issues/entry?template=Autoroller+Bug

Documentation for the AutoRoller is here:
https://skia.googlesource.com/buildbot/+/master/autoroll/README.md

CQ_INCLUDE_TRYBOTS=luci.chromium.try:android_optional_gpu_tests_rel;luci.chromium.try:linux-blink-rel;luci.chromium.try:linux-chromeos-compile-dbg;luci.chromium.try:linux_optional_gpu_tests_rel;luci.chromium.try:mac_optional_gpu_tests_rel;luci.chromium.try:win_optional_gpu_tests_rel
TBR=mtklein@google.com

Bug: None
Change-Id: I6b536048699ec036c8e329cad557c04d975b8088
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1799143Reviewed-by: chromium-autoroll <chromium-autoroll@skia-public.iam.gserviceaccount.com>
Commit-Queue: chromium-autoroll <chromium-autoroll@skia-public.iam.gserviceaccount.com>
Cr-Commit-Position: refs/heads/master@{#695805}

DEPS

@@ -162,7 +162,7 @@ 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': '3c70f9acfc33cefc1dc73f0d77faa9172755165c',
+  'skia_revision': 'f7cf794890d4ba978152c5da05eaa9a53b4f05d9',
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling V8
   # and whatever else without interference from each other.