Roll Skia from 7c1967700b44 to 439709a97dfd (8 revisions) (flutter#19712)

https://skia.googlesource.com/skia.git/+log/7c1967700b44..439709a97dfd

2020-07-13 dnfield@google.com Expose multi-frame methods for SkCodecImageGenerator
2020-07-13 brianosman@google.com Use stable sort for Viewer's help screen
2020-07-13 herb@google.com improve the speed of empty GrTextBlobs
2020-07-13 herb@google.com move drawTextPaths from RTC to SubRun
2020-07-13 johnstiles@google.com Replace ModulateRGBA effect with Xfermode using modulate blend.
2020-07-13 johnstiles@google.com Replace ModulateAlpha effect with Xfermode using src-in blend.
2020-07-13 brianosman@google.com SkRuntimeEffect: Guard against programs with no "main"
2020-07-13 adlai@google.com Make GrAsDirectContext public

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/+doc/master/autoroll/README.md

Author: skia-flutter-autoroll

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': '7c1967700b44cc0087bc78c347f90b2efa1fd122',
+  'skia_revision': '439709a97dfd168ef3d4ff08d15ff927f155fc10',
 
   # 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: 95df28233cb82e48bc0e4597a95ef320
+Signature: 874bcab3f8b26f94d0e9bb77eb61a6c7
 
 UNUSED LICENSES:
 
@@ -5312,18 +5312,12 @@ FILE: ../../../third_party/skia/src/gpu/dawn/GrDawnStagingBuffer.h
 FILE: ../../../third_party/skia/src/gpu/effects/GrArithmeticProcessor.fp
 FILE: ../../../third_party/skia/src/gpu/effects/GrDitherEffect.fp
 FILE: ../../../third_party/skia/src/gpu/effects/GrHighContrastFilterEffect.fp
-FILE: ../../../third_party/skia/src/gpu/effects/GrModulateAlphaEffect.fp
-FILE: ../../../third_party/skia/src/gpu/effects/GrModulateRGBAEffect.fp
 FILE: ../../../third_party/skia/src/gpu/effects/generated/GrArithmeticProcessor.cpp
 FILE: ../../../third_party/skia/src/gpu/effects/generated/GrArithmeticProcessor.h
 FILE: ../../../third_party/skia/src/gpu/effects/generated/GrDitherEffect.cpp
 FILE: ../../../third_party/skia/src/gpu/effects/generated/GrDitherEffect.h
 FILE: ../../../third_party/skia/src/gpu/effects/generated/GrHighContrastFilterEffect.cpp
 FILE: ../../../third_party/skia/src/gpu/effects/generated/GrHighContrastFilterEffect.h
-FILE: ../../../third_party/skia/src/gpu/effects/generated/GrModulateAlphaEffect.cpp
-FILE: ../../../third_party/skia/src/gpu/effects/generated/GrModulateAlphaEffect.h
-FILE: ../../../third_party/skia/src/gpu/effects/generated/GrModulateRGBAEffect.cpp
-FILE: ../../../third_party/skia/src/gpu/effects/generated/GrModulateRGBAEffect.h
 FILE: ../../../third_party/skia/src/gpu/ops/GrSimpleMeshDrawOpHelperWithStencil.cpp
 FILE: ../../../third_party/skia/src/gpu/ops/GrSimpleMeshDrawOpHelperWithStencil.h
 FILE: ../../../third_party/skia/src/gpu/tessellate/GrDrawAtlasPathOp.cpp