Roll src/third_party/skia 7ac038f..6791ee2 (20 commits) (flutter#15141)

https://skia.googlesource.com/skia.git/+log/7ac038f302f2..6791ee2f8059

git log 7ac038f..6791ee2 --date=short --first-parent --format='%ad %ae %s'
2020-01-04 rosasco@google.com Add logger service.
2020-01-03 herb@google.com Use fCurrGlyph as the looping variable.
2020-01-03 recipe-mega-autoroller@chops-service-accounts.iam.gserviceaccount.com Roll recipe dependencies (trivial).
2020-01-03 nifong@google.com Support using an externally manage list of images in UrlDataManager for wasm debugger.
2020-01-03 mtklein@google.com remove FAAA/FSAA bots
2020-01-03 mtklein@google.com remove redundant Debug bots that have ASAN bots
2020-01-03 bsalomon@google.com Some GrTypes cleanup.
2020-01-03 brianosman@google.com Remove SkRuntimeColorFilterFactory
2020-01-03 benjaminwagner@google.com [infra] Upgrade Win to 2019
2020-01-03 egdaniel@google.com Updated proxy isProtected to return a GrProtected enum.
2020-01-03 mtklein@google.com remove almost all Release ASAN bots
2020-01-03 brianosman@google.com split CPU BonusConfigs SAN bots out explicitly
2020-01-03 ethannicholas@google.com SkSL description methods are now only present in debug mode
2020-01-03 skia-autoroll@skia-public.iam.gserviceaccount.com Roll skia/third_party/skcms ab3cf9c7bd22..605b00d7728f (1 commits)
2020-01-03 brianosman@google.com Tweak the CanvasKit interface to SkRuntimeEffect
2020-01-03 mtklein@google.com one more flourish
2020-01-03 skia-autoroll@skia-public.iam.gserviceaccount.com Roll third_party/externals/angle2 cbbfa2f..1fdf6ca (1 commits)
2020-01-03 mtklein@google.com ultimate retry for image shader cleanup
2020-01-03 skia-autoroll@skia-public.iam.gserviceaccount.com Roll ../src 81693dc9aabc..a12a9d87841e (186 commits)
2020-01-03 benjaminwagner@google.com [infra] Use POSIX paths for Docker containers

Created with:
  gclient setdep -r src/third_party/skia@6791ee2f8059

If this roll has caused a breakage, revert this CL and stop the roller
using the controls here:
https://autoroll.skia.org/r/skia-flutter-autoroll
Please CC nifong@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

Bug: None
Tbr: nifong@google.com

DEPS

@@ -26,7 +26,7 @@ vars = {
   'skia_git': 'https://skia.googlesource.com',
   # OCMock is for testing only so there is no google clone
   'ocmock_git': 'https://github.com/erikdoe/ocmock.git',
-  'skia_revision': '7ac038f302f226bbab6701b5394e6cbb52582e61',
+  'skia_revision': '6791ee2f8059c6b395e116011fb8e68621cebe6c',
 
   # When updating the Dart revision, ensure that all entries that are
   # dependencies of Dart are also updated to match the entries in the

ci/licenses_golden/licenses_skia

@@ -1,4 +1,4 @@
-Signature: 71b562681ce8535932dc0026c96f9cfd
+Signature: 436cc8b3ba6a55cf0460ae23489d29e1
 
 UNUSED LICENSES:
 
@@ -2970,7 +2970,6 @@ FILE: ../../../third_party/skia/modules/skresources/include/SkResources.h
 FILE: ../../../third_party/skia/modules/skresources/src/SkResources.cpp
 FILE: ../../../third_party/skia/samplecode/SampleBackdropBounds.cpp
 FILE: ../../../third_party/skia/samplecode/SampleImageFilterDAG.cpp
-FILE: ../../../third_party/skia/src/core/SkColorFilterPriv.h
 FILE: ../../../third_party/skia/src/core/SkImageFilterTypes.cpp
 FILE: ../../../third_party/skia/src/core/SkImageFilterTypes.h
 FILE: ../../../third_party/skia/src/core/SkImageFilter_Base.h