Added comment about repeated responses

src/proto/grpc/reflection/v1alpha/reflection.proto

@@ -94,6 +94,8 @@ message ServerReflectionResponse {
     // file_containing_extension requests with transitive dependencies. As
     // the repeated label is not allowed in oneof fields, we use a
     // FileDescriptorResponse message to encapsulate the repeated fields.
+    // The reflection service is allowed to avoid sending FileDescriptorProtos
+    // that were previously sent in response to earlier requests in the stream.
     FileDescriptorResponse file_descriptor_response = 4;
 
     // This message is used to answer all_extension_numbers_of_type requst.