Revert "Add ALTS C stack to gRPC core"
diff --git a/gRPC-Core.podspec b/gRPC-Core.podspec
index 7f61719..6c6c769 100644
--- a/gRPC-Core.podspec
+++ b/gRPC-Core.podspec
@@ -93,7 +93,7 @@
   }
 
   s.default_subspecs = 'Interface', 'Implementation'
-  s.compiler_flags = '-DGRPC_ARES=0', '-DPB_FIELD_16BIT'
+  s.compiler_flags = '-DGRPC_ARES=0'
   s.libraries = 'c++'
 
   # Like many other C libraries, gRPC-Core has its public headers under `include/<libname>/` and its
@@ -271,7 +271,6 @@
                       'src/core/ext/filters/http/message_compress/message_compress_filter.h',
                       'src/core/ext/filters/http/server/http_server_filter.h',
                       'src/core/lib/security/context/security_context.h',
-                      'src/core/lib/security/credentials/alts/alts_credentials.h',
                       'src/core/lib/security/credentials/composite/composite_credentials.h',
                       'src/core/lib/security/credentials/credentials.h',
                       'src/core/lib/security/credentials/fake/fake_credentials.h',
@@ -283,7 +282,6 @@
                       'src/core/lib/security/credentials/oauth2/oauth2_credentials.h',
                       'src/core/lib/security/credentials/plugin/plugin_credentials.h',
                       'src/core/lib/security/credentials/ssl/ssl_credentials.h',
-                      'src/core/lib/security/security_connector/alts_security_connector.h',
                       'src/core/lib/security/security_connector/security_connector.h',
                       'src/core/lib/security/transport/auth_filters.h',
                       'src/core/lib/security/transport/secure_endpoint.h',
@@ -291,35 +289,15 @@
                       'src/core/lib/security/transport/target_authority_table.h',
                       'src/core/lib/security/transport/tsi_error.h',
                       'src/core/lib/security/util/json_util.h',
-                      'src/core/tsi/alts/crypt/gsec.h',
-                      'src/core/tsi/alts/frame_protector/alts_counter.h',
-                      'src/core/tsi/alts/frame_protector/alts_crypter.h',
-                      'src/core/tsi/alts/frame_protector/alts_frame_protector.h',
-                      'src/core/tsi/alts/frame_protector/alts_record_protocol_crypter_common.h',
-                      'src/core/tsi/alts/frame_protector/frame_handler.h',
-                      'src/core/tsi/alts/handshaker/alts_handshaker_client.h',
-                      'src/core/tsi/alts/handshaker/alts_tsi_event.h',
-                      'src/core/tsi/alts/handshaker/alts_tsi_handshaker.h',
-                      'src/core/tsi/alts/handshaker/alts_tsi_handshaker_private.h',
-                      'src/core/tsi/alts/zero_copy_frame_protector/alts_grpc_integrity_only_record_protocol.h',
-                      'src/core/tsi/alts/zero_copy_frame_protector/alts_grpc_privacy_integrity_record_protocol.h',
-                      'src/core/tsi/alts/zero_copy_frame_protector/alts_grpc_record_protocol.h',
-                      'src/core/tsi/alts/zero_copy_frame_protector/alts_grpc_record_protocol_common.h',
-                      'src/core/tsi/alts/zero_copy_frame_protector/alts_iovec_record_protocol.h',
-                      'src/core/tsi/alts/zero_copy_frame_protector/alts_zero_copy_grpc_protector.h',
-                      'src/core/lib/security/credentials/alts/check_gcp_environment.h',
-                      'src/core/lib/security/credentials/alts/grpc_alts_credentials_options.h',
-                      'src/core/tsi/alts/handshaker/alts_handshaker_service_api.h',
-                      'src/core/tsi/alts/handshaker/alts_handshaker_service_api_util.h',
-                      'src/core/tsi/alts/handshaker/alts_tsi_utils.h',
-                      'src/core/tsi/alts/handshaker/transport_security_common_api.h',
-                      'src/core/tsi/alts/handshaker/altscontext.pb.h',
-                      'src/core/tsi/alts/handshaker/handshaker.pb.h',
-                      'src/core/tsi/alts/handshaker/transport_security_common.pb.h',
+                      'src/core/tsi/alts_transport_security.h',
+                      'src/core/tsi/fake_transport_security.h',
+                      'src/core/tsi/ssl_transport_security.h',
+                      'src/core/tsi/ssl_types.h',
+                      'src/core/tsi/transport_security_grpc.h',
                       'src/core/tsi/transport_security.h',
                       'src/core/tsi/transport_security_adapter.h',
                       'src/core/tsi/transport_security_interface.h',
-                      'src/core/ext/transport/chttp2/client/chttp2_connector.h',
+                      'src/core/ext/transport/chttp2/server/chttp2_server.h',
                       'src/core/ext/filters/client_channel/backup_poller.h',
                       'src/core/ext/filters/client_channel/client_channel.h',
                       'src/core/ext/filters/client_channel/client_channel_factory.h',
@@ -342,12 +320,7 @@
                       'src/core/ext/filters/client_channel/subchannel_index.h',
                       'src/core/ext/filters/client_channel/uri_parser.h',
                       'src/core/ext/filters/deadline/deadline_filter.h',
-                      'src/core/tsi/alts_transport_security.h',
-                      'src/core/tsi/fake_transport_security.h',
-                      'src/core/tsi/ssl_transport_security.h',
-                      'src/core/tsi/ssl_types.h',
-                      'src/core/tsi/transport_security_grpc.h',
-                      'src/core/ext/transport/chttp2/server/chttp2_server.h',
+                      'src/core/ext/transport/chttp2/client/chttp2_connector.h',
                       'src/core/ext/transport/inproc/inproc_transport.h',
                       'src/core/lib/avl/avl.h',
                       'src/core/lib/backoff/backoff.h',
@@ -658,7 +631,6 @@
                       'src/core/ext/filters/http/server/http_server_filter.cc',
                       'src/core/lib/http/httpcli_security_connector.cc',
                       'src/core/lib/security/context/security_context.cc',
-                      'src/core/lib/security/credentials/alts/alts_credentials.cc',
                       'src/core/lib/security/credentials/composite/composite_credentials.cc',
                       'src/core/lib/security/credentials/credentials.cc',
                       'src/core/lib/security/credentials/credentials_metadata.cc',
@@ -672,7 +644,6 @@
                       'src/core/lib/security/credentials/oauth2/oauth2_credentials.cc',
                       'src/core/lib/security/credentials/plugin/plugin_credentials.cc',
                       'src/core/lib/security/credentials/ssl/ssl_credentials.cc',
-                      'src/core/lib/security/security_connector/alts_security_connector.cc',
                       'src/core/lib/security/security_connector/security_connector.cc',
                       'src/core/lib/security/transport/client_auth_filter.cc',
                       'src/core/lib/security/transport/secure_endpoint.cc',
@@ -682,42 +653,14 @@
                       'src/core/lib/security/transport/tsi_error.cc',
                       'src/core/lib/security/util/json_util.cc',
                       'src/core/lib/surface/init_secure.cc',
-                      'src/core/tsi/alts/crypt/aes_gcm.cc',
-                      'src/core/tsi/alts/crypt/gsec.cc',
-                      'src/core/tsi/alts/frame_protector/alts_counter.cc',
-                      'src/core/tsi/alts/frame_protector/alts_crypter.cc',
-                      'src/core/tsi/alts/frame_protector/alts_frame_protector.cc',
-                      'src/core/tsi/alts/frame_protector/alts_record_protocol_crypter_common.cc',
-                      'src/core/tsi/alts/frame_protector/alts_seal_privacy_integrity_crypter.cc',
-                      'src/core/tsi/alts/frame_protector/alts_unseal_privacy_integrity_crypter.cc',
-                      'src/core/tsi/alts/frame_protector/frame_handler.cc',
-                      'src/core/tsi/alts/handshaker/alts_handshaker_client.cc',
-                      'src/core/tsi/alts/handshaker/alts_tsi_event.cc',
-                      'src/core/tsi/alts/handshaker/alts_tsi_handshaker.cc',
-                      'src/core/tsi/alts/zero_copy_frame_protector/alts_grpc_integrity_only_record_protocol.cc',
-                      'src/core/tsi/alts/zero_copy_frame_protector/alts_grpc_privacy_integrity_record_protocol.cc',
-                      'src/core/tsi/alts/zero_copy_frame_protector/alts_grpc_record_protocol_common.cc',
-                      'src/core/tsi/alts/zero_copy_frame_protector/alts_iovec_record_protocol.cc',
-                      'src/core/tsi/alts/zero_copy_frame_protector/alts_zero_copy_grpc_protector.cc',
-                      'src/core/lib/security/credentials/alts/check_gcp_environment.cc',
-                      'src/core/lib/security/credentials/alts/check_gcp_environment_linux.cc',
-                      'src/core/lib/security/credentials/alts/check_gcp_environment_no_op.cc',
-                      'src/core/lib/security/credentials/alts/check_gcp_environment_windows.cc',
-                      'src/core/lib/security/credentials/alts/grpc_alts_credentials_client_options.cc',
-                      'src/core/lib/security/credentials/alts/grpc_alts_credentials_options.cc',
-                      'src/core/lib/security/credentials/alts/grpc_alts_credentials_server_options.cc',
-                      'src/core/tsi/alts/handshaker/alts_handshaker_service_api.cc',
-                      'src/core/tsi/alts/handshaker/alts_handshaker_service_api_util.cc',
-                      'src/core/tsi/alts/handshaker/alts_tsi_utils.cc',
-                      'src/core/tsi/alts/handshaker/transport_security_common_api.cc',
-                      'src/core/tsi/alts/handshaker/altscontext.pb.c',
-                      'src/core/tsi/alts/handshaker/handshaker.pb.c',
-                      'src/core/tsi/alts/handshaker/transport_security_common.pb.c',
+                      'src/core/tsi/alts_transport_security.cc',
+                      'src/core/tsi/fake_transport_security.cc',
+                      'src/core/tsi/ssl_transport_security.cc',
+                      'src/core/tsi/transport_security_grpc.cc',
                       'src/core/tsi/transport_security.cc',
                       'src/core/tsi/transport_security_adapter.cc',
-                      'src/core/ext/transport/chttp2/client/insecure/channel_create.cc',
-                      'src/core/ext/transport/chttp2/client/insecure/channel_create_posix.cc',
-                      'src/core/ext/transport/chttp2/client/chttp2_connector.cc',
+                      'src/core/ext/transport/chttp2/server/chttp2_server.cc',
+                      'src/core/ext/transport/chttp2/client/secure/secure_channel_create.cc',
                       'src/core/ext/filters/client_channel/backup_poller.cc',
                       'src/core/ext/filters/client_channel/channel_connectivity.cc',
                       'src/core/ext/filters/client_channel/client_channel.cc',
@@ -741,14 +684,11 @@
                       'src/core/ext/filters/client_channel/subchannel_index.cc',
                       'src/core/ext/filters/client_channel/uri_parser.cc',
                       'src/core/ext/filters/deadline/deadline_filter.cc',
-                      'src/core/tsi/alts_transport_security.cc',
-                      'src/core/tsi/fake_transport_security.cc',
-                      'src/core/tsi/ssl_transport_security.cc',
-                      'src/core/tsi/transport_security_grpc.cc',
-                      'src/core/ext/transport/chttp2/server/chttp2_server.cc',
-                      'src/core/ext/transport/chttp2/client/secure/secure_channel_create.cc',
+                      'src/core/ext/transport/chttp2/client/chttp2_connector.cc',
                       'src/core/ext/transport/chttp2/server/insecure/server_chttp2.cc',
                       'src/core/ext/transport/chttp2/server/insecure/server_chttp2_posix.cc',
+                      'src/core/ext/transport/chttp2/client/insecure/channel_create.cc',
+                      'src/core/ext/transport/chttp2/client/insecure/channel_create_posix.cc',
                       'src/core/ext/transport/inproc/inproc_plugin.cc',
                       'src/core/ext/transport/inproc/inproc_transport.cc',
                       'src/core/ext/filters/client_channel/lb_policy/grpclb/client_load_reporting_filter.cc',
@@ -825,7 +765,6 @@
                               'src/core/ext/filters/http/message_compress/message_compress_filter.h',
                               'src/core/ext/filters/http/server/http_server_filter.h',
                               'src/core/lib/security/context/security_context.h',
-                              'src/core/lib/security/credentials/alts/alts_credentials.h',
                               'src/core/lib/security/credentials/composite/composite_credentials.h',
                               'src/core/lib/security/credentials/credentials.h',
                               'src/core/lib/security/credentials/fake/fake_credentials.h',
@@ -837,7 +776,6 @@
                               'src/core/lib/security/credentials/oauth2/oauth2_credentials.h',
                               'src/core/lib/security/credentials/plugin/plugin_credentials.h',
                               'src/core/lib/security/credentials/ssl/ssl_credentials.h',
-                              'src/core/lib/security/security_connector/alts_security_connector.h',
                               'src/core/lib/security/security_connector/security_connector.h',
                               'src/core/lib/security/transport/auth_filters.h',
                               'src/core/lib/security/transport/secure_endpoint.h',
@@ -845,35 +783,15 @@
                               'src/core/lib/security/transport/target_authority_table.h',
                               'src/core/lib/security/transport/tsi_error.h',
                               'src/core/lib/security/util/json_util.h',
-                              'src/core/tsi/alts/crypt/gsec.h',
-                              'src/core/tsi/alts/frame_protector/alts_counter.h',
-                              'src/core/tsi/alts/frame_protector/alts_crypter.h',
-                              'src/core/tsi/alts/frame_protector/alts_frame_protector.h',
-                              'src/core/tsi/alts/frame_protector/alts_record_protocol_crypter_common.h',
-                              'src/core/tsi/alts/frame_protector/frame_handler.h',
-                              'src/core/tsi/alts/handshaker/alts_handshaker_client.h',
-                              'src/core/tsi/alts/handshaker/alts_tsi_event.h',
-                              'src/core/tsi/alts/handshaker/alts_tsi_handshaker.h',
-                              'src/core/tsi/alts/handshaker/alts_tsi_handshaker_private.h',
-                              'src/core/tsi/alts/zero_copy_frame_protector/alts_grpc_integrity_only_record_protocol.h',
-                              'src/core/tsi/alts/zero_copy_frame_protector/alts_grpc_privacy_integrity_record_protocol.h',
-                              'src/core/tsi/alts/zero_copy_frame_protector/alts_grpc_record_protocol.h',
-                              'src/core/tsi/alts/zero_copy_frame_protector/alts_grpc_record_protocol_common.h',
-                              'src/core/tsi/alts/zero_copy_frame_protector/alts_iovec_record_protocol.h',
-                              'src/core/tsi/alts/zero_copy_frame_protector/alts_zero_copy_grpc_protector.h',
-                              'src/core/lib/security/credentials/alts/check_gcp_environment.h',
-                              'src/core/lib/security/credentials/alts/grpc_alts_credentials_options.h',
-                              'src/core/tsi/alts/handshaker/alts_handshaker_service_api.h',
-                              'src/core/tsi/alts/handshaker/alts_handshaker_service_api_util.h',
-                              'src/core/tsi/alts/handshaker/alts_tsi_utils.h',
-                              'src/core/tsi/alts/handshaker/transport_security_common_api.h',
-                              'src/core/tsi/alts/handshaker/altscontext.pb.h',
-                              'src/core/tsi/alts/handshaker/handshaker.pb.h',
-                              'src/core/tsi/alts/handshaker/transport_security_common.pb.h',
+                              'src/core/tsi/alts_transport_security.h',
+                              'src/core/tsi/fake_transport_security.h',
+                              'src/core/tsi/ssl_transport_security.h',
+                              'src/core/tsi/ssl_types.h',
+                              'src/core/tsi/transport_security_grpc.h',
                               'src/core/tsi/transport_security.h',
                               'src/core/tsi/transport_security_adapter.h',
                               'src/core/tsi/transport_security_interface.h',
-                              'src/core/ext/transport/chttp2/client/chttp2_connector.h',
+                              'src/core/ext/transport/chttp2/server/chttp2_server.h',
                               'src/core/ext/filters/client_channel/backup_poller.h',
                               'src/core/ext/filters/client_channel/client_channel.h',
                               'src/core/ext/filters/client_channel/client_channel_factory.h',
@@ -896,12 +814,7 @@
                               'src/core/ext/filters/client_channel/subchannel_index.h',
                               'src/core/ext/filters/client_channel/uri_parser.h',
                               'src/core/ext/filters/deadline/deadline_filter.h',
-                              'src/core/tsi/alts_transport_security.h',
-                              'src/core/tsi/fake_transport_security.h',
-                              'src/core/tsi/ssl_transport_security.h',
-                              'src/core/tsi/ssl_types.h',
-                              'src/core/tsi/transport_security_grpc.h',
-                              'src/core/ext/transport/chttp2/server/chttp2_server.h',
+                              'src/core/ext/transport/chttp2/client/chttp2_connector.h',
                               'src/core/ext/transport/inproc/inproc_transport.h',
                               'src/core/lib/avl/avl.h',
                               'src/core/lib/backoff/backoff.h',
@@ -1062,15 +975,8 @@
 
     ss.source_files = 'src/core/ext/transport/cronet/client/secure/cronet_channel_create.cc',
                       'src/core/ext/transport/cronet/transport/cronet_transport.cc',
-                      'third_party/nanopb/pb_common.c',
-                      'third_party/nanopb/pb_decode.c',
-                      'third_party/nanopb/pb_encode.c',
                       'src/core/ext/transport/cronet/transport/cronet_transport.h',
-                      'third_party/objective_c/Cronet/bidirectional_stream_c.h',
-                      'third_party/nanopb/pb.h',
-                      'third_party/nanopb/pb_common.h',
-                      'third_party/nanopb/pb_decode.h',
-                      'third_party/nanopb/pb_encode.h'
+                      'third_party/objective_c/Cronet/bidirectional_stream_c.h'
   end
 
   s.subspec 'Tests' do |ss|