Roll src/third_party/skia df640e6..8c6c8b0 (12 commits) (#13098)

https://skia.googlesource.com/skia.git/+log/df640e6d14a5..8c6c8b0c42e2

git log df640e6..8c6c8b0 --date=short --no-merges --format='%ad %ae %s'
2019-10-11 recipe-mega-autoroller@chops-service-accounts.iam.gserviceaccount.com Roll recipe dependencies (trivial).
2019-10-11 halcanary@google.com docs/fiddle: add "incomplete" fiddle.
2019-10-11 halcanary@google.com SkPDF/tests: add regression test for crbug/494913
2019-10-11 recipe-mega-autoroller@chops-service-accounts.iam.gserviceaccount.com Roll recipe dependencies (trivial).
2019-10-11 egdaniel@google.com Remove GrPixelConfig version of CompressedDataSize.
2019-10-11 halcanary@google.com Docs: Update docs to point at named fiddles
2019-10-11 recipe-mega-autoroller@chops-service-accounts.iam.gserviceaccount.com Roll recipe dependencies (trivial).
2019-10-11 herb@google.com Introduce SkGlyphDrawableBuffer
2019-10-11 recipe-mega-autoroller@chops-service-accounts.iam.gserviceaccount.com Roll recipe dependencies (trivial).
2019-10-11 borenet@google.com [infra] Fix presubmit by pinning tools/build
2019-10-11 egdaniel@google.com Fix GL RGB format bytes per pixel.
2019-10-11 skia-autoroll@skia-public.iam.gserviceaccount.com Roll third_party/externals/angle2 5d9c4ee..67486ec (18 commits)

Created with:
  gclient setdep -r src/third_party/skia@8c6c8b0c42e2

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 kjlubick@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=kjlubick@google.com

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': 'df640e6d14a55e8331786a6dbe4492cb6bffa576',
+  'skia_revision': '8c6c8b0c42e2e3d92d596bc950aedfecdd814d5d',
 
   # 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: aca5dfed087e4f09384c45ff3b7569d3
+Signature: 7e1c50b87af7396c0f85b3bf776a0ea5
 
 UNUSED LICENSES:
 
@@ -3320,6 +3320,8 @@ FILE: ../../../third_party/skia/src/core/SkDescriptor.cpp
 FILE: ../../../third_party/skia/src/core/SkDraw_atlas.cpp
 FILE: ../../../third_party/skia/src/core/SkEffectPriv.h
 FILE: ../../../third_party/skia/src/core/SkEnumerate.h
+FILE: ../../../third_party/skia/src/core/SkGlyphBuffer.cpp
+FILE: ../../../third_party/skia/src/core/SkGlyphBuffer.h
 FILE: ../../../third_party/skia/src/core/SkPathMakers.h
 FILE: ../../../third_party/skia/src/core/SkStrikeForGPU.cpp
 FILE: ../../../third_party/skia/src/core/SkStrikeForGPU.h
@@ -4967,6 +4969,7 @@ FILE: ../../../third_party/skia/docs/examples/Text_Size.cpp
 FILE: ../../../third_party/skia/docs/examples/Text_Skew_X.cpp
 FILE: ../../../third_party/skia/docs/examples/Typeface_Methods.cpp
 FILE: ../../../third_party/skia/docs/examples/Xor.cpp
+FILE: ../../../third_party/skia/docs/examples/incomplete.cpp
 FILE: ../../../third_party/skia/experimental/minimal_ios_mtl_skia_app/main.mm
 FILE: ../../../third_party/skia/experimental/skottie_ios/SkMetalViewBridge.h
 FILE: ../../../third_party/skia/experimental/skottie_ios/SkMetalViewBridge.mm