[#2006] Correctly handle HttpMessage / HttpContent implementations

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

@@ -149,8 +149,13 @@ public abstract class HttpContentEncoder extends MessageToMessageCodec<HttpReque
                 } else {
                     out.add(res);
                     state = State.AWAIT_CONTENT;
+                    if (!(msg instanceof HttpContent)) {
+                        // only break out the switch statement if we have not content to process
+                        // See https://github.com/netty/netty/issues/2006
                         break;
                     }
+                    // Fall through to encode the content
+                }
             }
             case AWAIT_CONTENT: {
                 ensureContent(msg);