Optionalize message_size_filter
diff --git a/grpc.gemspec b/grpc.gemspec
index a3a5870..60fc0a2 100755
--- a/grpc.gemspec
+++ b/grpc.gemspec
@@ -183,7 +183,6 @@
   s.files += %w( src/core/lib/channel/handshaker_registry.h )
   s.files += %w( src/core/lib/channel/http_client_filter.h )
   s.files += %w( src/core/lib/channel/http_server_filter.h )
-  s.files += %w( src/core/lib/channel/message_size_filter.h )
   s.files += %w( src/core/lib/compression/algorithm_metadata.h )
   s.files += %w( src/core/lib/compression/message_compress.h )
   s.files += %w( src/core/lib/debug/trace.h )
@@ -373,6 +372,7 @@
   s.files += %w( src/core/ext/census/trace_string.h )
   s.files += %w( src/core/ext/census/tracing.h )
   s.files += %w( src/core/ext/filters/max_age/max_age_filter.h )
+  s.files += %w( src/core/ext/filters/message_size/message_size_filter.h )
   s.files += %w( src/core/lib/surface/init.c )
   s.files += %w( src/core/lib/channel/channel_args.c )
   s.files += %w( src/core/lib/channel/channel_stack.c )
@@ -385,7 +385,6 @@
   s.files += %w( src/core/lib/channel/handshaker_registry.c )
   s.files += %w( src/core/lib/channel/http_client_filter.c )
   s.files += %w( src/core/lib/channel/http_server_filter.c )
-  s.files += %w( src/core/lib/channel/message_size_filter.c )
   s.files += %w( src/core/lib/compression/compression.c )
   s.files += %w( src/core/lib/compression/message_compress.c )
   s.files += %w( src/core/lib/debug/trace.c )
@@ -605,6 +604,7 @@
   s.files += %w( src/core/ext/census/trace_context.c )
   s.files += %w( src/core/ext/census/tracing.c )
   s.files += %w( src/core/ext/filters/max_age/max_age_filter.c )
+  s.files += %w( src/core/ext/filters/message_size/message_size_filter.c )
   s.files += %w( src/core/plugin_registry/grpc_plugin_registry.c )
   s.files += %w( third_party/boringssl/crypto/aes/internal.h )
   s.files += %w( third_party/boringssl/crypto/asn1/asn1_locl.h )