Add a subchannel factory decorator library
diff --git a/gRPC.podspec b/gRPC.podspec
index 8cb4e9a..79c9235 100644
--- a/gRPC.podspec
+++ b/gRPC.podspec
@@ -173,6 +173,8 @@
                       'src/core/client_config/resolvers/sockaddr_resolver.h',
                       'src/core/client_config/subchannel.h',
                       'src/core/client_config/subchannel_factory.h',
+                      'src/core/client_config/subchannel_factory_decorators/add_channel_arg.h',
+                      'src/core/client_config/subchannel_factory_decorators/merge_channel_args.h',
                       'src/core/client_config/uri_parser.h',
                       'src/core/compression/message_compress.h',
                       'src/core/debug/trace.h',
@@ -300,6 +302,8 @@
                       'src/core/client_config/resolvers/sockaddr_resolver.c',
                       'src/core/client_config/subchannel.c',
                       'src/core/client_config/subchannel_factory.c',
+                      'src/core/client_config/subchannel_factory_decorators/add_channel_arg.c',
+                      'src/core/client_config/subchannel_factory_decorators/merge_channel_args.c',
                       'src/core/client_config/uri_parser.c',
                       'src/core/compression/algorithm.c',
                       'src/core/compression/message_compress.c',
@@ -440,6 +444,8 @@
                               'src/core/client_config/resolvers/sockaddr_resolver.h',
                               'src/core/client_config/subchannel.h',
                               'src/core/client_config/subchannel_factory.h',
+                              'src/core/client_config/subchannel_factory_decorators/add_channel_arg.h',
+                              'src/core/client_config/subchannel_factory_decorators/merge_channel_args.h',
                               'src/core/client_config/uri_parser.h',
                               'src/core/compression/message_compress.h',
                               'src/core/debug/trace.h',