diff --git a/vendor/google.golang.org/grpc/encoding/encoding.go b/vendor/google.golang.org/grpc/encoding/encoding.go
index 30a75da..195e844 100644
--- a/vendor/google.golang.org/grpc/encoding/encoding.go
+++ b/vendor/google.golang.org/grpc/encoding/encoding.go
@@ -46,6 +46,10 @@
 	// coding header.  The result must be static; the result cannot change
 	// between calls.
 	Name() string
+	// EXPERIMENTAL: if a Compressor implements
+	// DecompressedSize(compressedBytes []byte) int, gRPC will call it
+	// to determine the size of the buffer allocated for the result of decompression.
+	// Return -1 to indicate unknown size.
 }
 
 var registeredCompressor = make(map[string]Compressor)