c7e3f6c merge error

Motivation:
Cherry-pick of c7e3f6c went wrong.

Modifications:
- Fix comiple error

Result:
Build completes.

codec-http/src/main/java/io/netty/handler/codec/http/HttpServerUpgradeHandler.java

@@ -298,7 +298,7 @@ private boolean upgrade(final ChannelHandlerContext ctx, final FullHttpRequest r
         }
 
         // Ensure that all required protocol-specific headers are found in the request.
-        for (String requiredHeader : requiredHeaders) {
+        for (CharSequence requiredHeader : requiredHeaders) {
             if (!request.headers().contains(requiredHeader)) {
                 return false;
             }