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

BUILD

CMakeLists.txt

Makefile

binding.gyp

build.yaml

cmake/msvc_static_runtime.cmake

composer.json

config.m4

doc/environment_variables.md

gRPC-Core.podspec

grpc.gemspec

include/grpc/impl/codegen/grpc_types.h

package.xml

src/core/ext/client_channel/client_channel.c

src/core/ext/client_channel/client_channel.h

src/core/ext/transport/chttp2/transport/chttp2_transport.c

src/core/ext/transport/chttp2/transport/frame_ping.c

src/core/ext/transport/chttp2/transport/frame_ping.h

src/core/ext/transport/chttp2/transport/frame_settings.c

...core/ext/transport/chttp2/transport/frame_window_update.c