Merge remote-tracking branch 'upstream/master'

BUILD

Makefile

build.yaml

include/grpc++/impl/codegen/method_handler_impl.h

include/grpc++/impl/server_builder_option.h

include/grpc++/impl/server_builder_plugin.h

include/grpc++/impl/server_initializer.h

include/grpc++/server.h

include/grpc++/server_builder.h

package.json

src/cpp/server/server.cc

src/cpp/server/server_builder.cc

src/csharp/Grpc.Examples.Tests/MathClientServerTests.cs

src/csharp/Grpc.Examples/MathExamples.cs

src/csharp/Grpc.Examples/MathServiceImpl.cs

src/csharp/Grpc.IntegrationTesting/StressTestClient.cs

src/node/tools/bin/protoc.js

src/node/tools/bin/protoc_plugin.js

src/proto/grpc/testing/echo_messages.proto

src/python/grpcio/tests/qps/benchmark_client.py