Remove deprecated call and TODO in Protocol negotiators

netty/src/main/java/io/grpc/netty/ProtocolNegotiator.java

@@ -32,7 +32,7 @@
 package io.grpc.netty;
 
 import io.grpc.Internal;
-import io.netty.channel.ChannelHandler;
+import io.netty.channel.ChannelInboundHandler;
 import io.netty.handler.codec.http2.Http2ConnectionHandler;
 import io.netty.util.AsciiString;
 
@@ -44,11 +44,8 @@ public interface ProtocolNegotiator {
 
   /**
    * The Netty handler to control the protocol negotiation.
-   *
-   * <p>TODO(carl-mastrangelo): Replace ChannelHandler with ChannelInboundHandler or
-   * ChannelOutboundHandler, since exceptionCaught is deprecated.
    */
-  interface Handler extends ChannelHandler {
+  interface Handler extends ChannelInboundHandler {
     /**
      * The HTTP/2 scheme to be used when sending {@code HEADERS}.
      */

netty/src/main/java/io/grpc/netty/ProtocolNegotiators.java

@@ -89,30 +89,20 @@ public final class ProtocolNegotiators {
     return new ProtocolNegotiator() {
       @Override
       public Handler newHandler(final Http2ConnectionHandler handler) {
-        return new Handler() {
+        class PlaintextHandler extends ChannelDuplexHandler implements Handler {
           @Override
           public void handlerAdded(ChannelHandlerContext ctx) throws Exception {
             // Just replace this handler with the gRPC handler.
             ctx.pipeline().replace(this, null, handler);
           }
 
-          @Override
-          public void handlerRemoved(ChannelHandlerContext ctx) throws Exception {
-            // Don't care.
-          }
-
-          @Override
-          @Deprecated
-          public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
-            // Should never happen.
-            ctx.fireExceptionCaught(cause);
-          }
-
           @Override
           public AsciiString scheme() {
             return Utils.HTTP;
           }
-        };
+        }
+
+        return new PlaintextHandler();
       }
     };
   }