Roll src/third_party/skia 7190399..6c3db04 (9 commits)

https://skia.googlesource.com/skia.git/+log/71903997254f..6c3db04c8b03

git log 7190399..6c3db04 --date=short --first-parent --format='%ad %ae %s'
2020-05-13 mtklein@google.com Revert "Add an implementation and log2 variants for Wang's formula"
2020-05-13 egdaniel@google.com Reland "Reland "Add api on GrContext to update the data of GrBackendTextures.""
2020-05-13 senorblanco@chromium.org Make staging manager lists private to GrGpu.
2020-05-13 egdaniel@google.com Pass externally synchronizaed flag to vulkan memory allocator.
2020-05-13 csmartdalton@google.com Add an implementation and log2 variants for Wang's formula
2020-05-13 adlai@google.com Enable kernel caching in GrMatrixConvolutionEffect
2020-05-13 bsalomon@google.com Add workaround for TecnoSpark 3 Pro MIP mapping
2020-05-13 egdaniel@google.com Add GrContext getter to SkSurface.
2020-05-13 michaelludwig@google.com Simplify GrClip::getConservativeBounds() signature

Created with:
  gclient setdep -r src/third_party/skia@6c3db04c8b03

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 jlavrova@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: jlavrova@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': '71903997254fae5c2aea09da631d9ccabd3722d8',
+  'skia_revision': '6c3db04c8b0331690b1a0a3e214093bc73469edd',
 
   # 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: 2a0db9ecd51d6b184f349d250fb30026
+Signature: f1e892ba3cafe47bf66e223634ac32f2
 
 UNUSED LICENSES: