Merge remote-tracking branch 'upstream/master' into fail_fast

BUILD

CMakeLists.txt

Makefile

build.yaml

composer.json

doc/PROTOCOL-HTTP2.md

doc/environment_variables.md

etc/roots.pem

examples/node/static_codegen/greeter_client.js

include/grpc++/ext/reflection.pb.h

src/compiler/php_generator.cc

src/compiler/php_generator.h

src/compiler/php_generator_helpers.h

src/compiler/php_plugin.cc

src/core/ext/client_config/client_channel.c

src/core/ext/client_config/lb_policy.h

src/core/ext/lb_policy/grpclb/grpclb.c

src/core/ext/resolver/dns/native/dns_resolver.c

src/core/ext/resolver/sockaddr/sockaddr_resolver.c

src/core/ext/transport/cronet/transport/cronet_transport.c