Add "identity" as a content encoding
Fixes grpc/grpc-common#257
diff --git a/doc/PROTOCOL-HTTP2.md b/doc/PROTOCOL-HTTP2.md
index 8075414..d4f1d0e 100644
--- a/doc/PROTOCOL-HTTP2.md
+++ b/doc/PROTOCOL-HTTP2.md
@@ -37,7 +37,7 @@
* **Microsecond** → "u"
* **Nanosecond** → "n"
* **Content-Type** → "content-type" "application/grpc" [("+proto" / "+json" / {_custom_})]
-* **Content-Coding** → "gzip" / "deflate" / "snappy" / {_custom_}
+* **Content-Coding** → "identity" / "gzip" / "deflate" / "snappy" / {_custom_}
* **Message-Encoding** → "grpc-encoding" Content-Coding
* **Message-Accept-Encoding** → "grpc-accept-encoding" Content-Coding \*("," Content-Coding)
* **User-Agent** → "user-agent" {_structured user-agent string_}