Roll Skia from 3d6bf04 to 637838d (2 revisions)

https://skia.googlesource.com/skia.git/+log/3d6bf04366f6..637838d20abd

2020-06-12 [email protected] Fix compiler warnings on Mac build.
2020-06-12 [email protected] Fix copyright

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 [email protected] 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': '3d6bf04366f6bb33b058b39066dd92334c185a66',
+  'skia_revision': '637838d20abd226f457c3b4f6791f5f01bd0cdb9',
 
   # 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: f80526dd737771501e0edc84c3944355
+Signature: f085cce4ad7add5df285ed5afca7c2db
 
 UNUSED LICENSES:
 
@@ -2458,7 +2458,6 @@ FILE: ../../../third_party/skia/src/gpu/GrDrawingManager.cpp
 FILE: ../../../third_party/skia/src/gpu/GrDrawingManager.h
 FILE: ../../../third_party/skia/src/gpu/GrFragmentProcessor.cpp
 FILE: ../../../third_party/skia/src/gpu/GrGpuResourcePriv.h
-FILE: ../../../third_party/skia/src/gpu/GrHashMapWithCache.h
 FILE: ../../../third_party/skia/src/gpu/GrManagedResource.h
 FILE: ../../../third_party/skia/src/gpu/GrNonAtomicRef.h
 FILE: ../../../third_party/skia/src/gpu/GrOpFlushState.cpp
@@ -5283,6 +5282,7 @@ FILE: ../../../third_party/skia/src/core/SkVerticesPriv.h
 FILE: ../../../third_party/skia/src/gpu/GrDynamicAtlas.cpp
 FILE: ../../../third_party/skia/src/gpu/GrDynamicAtlas.h
 FILE: ../../../third_party/skia/src/gpu/GrEagerVertexAllocator.h
+FILE: ../../../third_party/skia/src/gpu/GrHashMapWithCache.h
 FILE: ../../../third_party/skia/src/gpu/GrStagingBuffer.cpp
 FILE: ../../../third_party/skia/src/gpu/GrStagingBuffer.h
 FILE: ../../../third_party/skia/src/gpu/ccpr/GrAutoMapVertexBuffer.h