Merge github.com:grpc/grpc into slice_with_exec_ctx

BUILD

CMakeLists.txt

Makefile

binding.gyp

build.yaml

config.m4

gRPC-Core.podspec

grpc.gemspec

package.xml

src/core/lib/channel/message_size_filter.c

src/core/lib/channel/message_size_filter.h

src/core/lib/surface/init.c

src/python/grpcio/grpc_core_dependencies.py

test/core/end2end/fuzzers/BUILD

test/core/end2end/generate_tests.bzl

tools/doxygen/Doxyfile.core.internal

tools/run_tests/generated/sources_and_headers.json

vsprojects/vcxproj/grpc/grpc.vcxproj

vsprojects/vcxproj/grpc/grpc.vcxproj.filters

vsprojects/vcxproj/grpc_test_util/grpc_test_util.vcxproj