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

BUILD

CMakeLists.txt

Makefile

binding.gyp

build.yaml

config.m4

examples/php/route_guide/run_route_guide_client.sh

gRPC-Core.podspec

grpc.gemspec

package.xml

src/core/ext/census/trace_context.c

src/core/ext/census/trace_context.h

src/core/ext/census/tracing.c

src/core/ext/client_config/client_channel.c

src/core/ext/client_config/client_channel.h

src/core/ext/client_config/lb_policy_factory.c

src/core/ext/client_config/lb_policy_factory.h

src/core/ext/client_config/resolver_factory.h

src/core/ext/client_config/resolver_registry.c

src/core/ext/client_config/resolver_registry.h