Merge github.com:grpc/grpc into connected-subchannel

BUILD

Makefile

binding.gyp

build.yaml

gRPC.podspec

package.json

src/core/census/context.h

src/core/client_config/resolvers/dns_resolver.c

...nt_config/subchannel_factory_decorators/add_channel_arg.c

...config/subchannel_factory_decorators/merge_channel_args.h

src/core/support/slice.c

src/core/transport/chttp2/frame_data.c

src/core/transport/chttp2/hpack_parser.c

src/core/transport/chttp2/varint.h

src/csharp/Grpc.Examples/Grpc.Examples.csproj

src/csharp/Grpc.HealthCheck/Grpc.HealthCheck.csproj

src/csharp/Grpc.HealthCheck/proto/health.proto

src/csharp/generate_proto_csharp.sh

src/node/health_check/health.js

src/node/health_check/health.proto