Configures HTTP2 pipeline with more proper way

Motivation:

When we use pipeline.replace and we still had ongoing inbound, then
there will be some problem that inbound message would go to wrong
handlers. So we add handler first, and remove self after add, so that
the next handler will be the correct one.

Modifications:

Uses remove after addAfter instead of replace.

Result:

Fixed netty#6881

codec-http2/src/main/java/io/netty/handler/codec/http2/CleartextHttp2ServerUpgradeHandler.java

@@ -89,8 +89,11 @@ protected void decode(ChannelHandlerContext ctx, ByteBuf in, List<Object> out) t
                 // following network traffic
                 ctx.pipeline()
                    .remove(httpServerCodec)
-                   .remove(httpServerUpgradeHandler)
-                   .replace(this, null, http2ServerHandler);
+                   .remove(httpServerUpgradeHandler);
+
+                ctx.pipeline().addAfter(ctx.name(), null, http2ServerHandler);
+                ctx.pipeline().remove(this);
+
                 ctx.fireUserEventTriggered(PriorKnowledgeUpgradeEvent.INSTANCE);
             }
         }

codec-http2/src/test/java/io/netty/handler/codec/http2/CleartextHttp2ServerUpgradeHandlerTest.java

@@ -17,8 +17,10 @@
 
 import io.netty.buffer.ByteBuf;
 import io.netty.buffer.Unpooled;
+import io.netty.channel.Channel;
 import io.netty.channel.ChannelHandlerContext;
 import io.netty.channel.ChannelInboundHandlerAdapter;
+import io.netty.channel.ChannelInitializer;
 import io.netty.channel.embedded.EmbeddedChannel;
 import io.netty.handler.codec.http.DefaultHttpHeaders;
 import io.netty.handler.codec.http.HttpMethod;
@@ -35,7 +37,6 @@
 import io.netty.util.CharsetUtil;
 import io.netty.util.ReferenceCountUtil;
 import org.junit.After;
-import org.junit.Before;
 import org.junit.Test;
 
 import java.util.ArrayList;
@@ -56,8 +57,7 @@ public class CleartextHttp2ServerUpgradeHandlerTest {
 
     private List<Object> userEvents;
 
-    @Before
-    public void setUp() {
+    private void setUpServerChannel() {
         frameListener = mock(Http2FrameListener.class);
 
         http2ConnectionHandler = new Http2ConnectionHandlerBuilder().frameListener(frameListener).build();
@@ -91,6 +91,8 @@ public void tearDown() throws Exception {
 
     @Test
     public void priorKnowledge() throws Exception {
+        setUpServerChannel();
+
         channel.writeInbound(Http2CodecUtil.connectionPrefaceBuf());
 
         ByteBuf settingsFrame = settingsFrameBuf();
@@ -109,6 +111,8 @@ public void priorKnowledge() throws Exception {
 
     @Test
     public void upgrade() throws Exception {
+        setUpServerChannel();
+
         String upgradeString = "GET / HTTP/1.1\r\n" +
                                "Host: example.com\r\n" +
                                "Connection: Upgrade, HTTP2-Settings\r\n" +
@@ -138,6 +142,8 @@ public void upgrade() throws Exception {
 
     @Test
     public void priorKnowledgeInFragments() throws Exception {
+        setUpServerChannel();
+
         ByteBuf connectionPreface = Http2CodecUtil.connectionPrefaceBuf();
         assertFalse(channel.writeInbound(connectionPreface.readBytes(5), connectionPreface));
 
@@ -156,6 +162,8 @@ public void priorKnowledgeInFragments() throws Exception {
 
     @Test
     public void downgrade() throws Exception {
+        setUpServerChannel();
+
         String requestString = "GET / HTTP/1.1\r\n" +
                          "Host: example.com\r\n\r\n";
         ByteBuf inbound = Unpooled.buffer().writeBytes(requestString.getBytes(CharsetUtil.US_ASCII));
@@ -175,6 +183,45 @@ public void downgrade() throws Exception {
         assertNull(channel.readInbound());
     }
 
+    @Test
+    public void usedHttp2Codec() throws Exception {
+        final Http2Codec http2Codec = new Http2CodecBuilder(true, new ChannelInitializer<Channel>() {
+            @Override
+            protected void initChannel(Channel ch) throws Exception {
+            }
+        }).build();
+        UpgradeCodecFactory upgradeCodecFactory = new UpgradeCodecFactory() {
+            @Override
+            public UpgradeCodec newUpgradeCodec(CharSequence protocol) {
+                return new Http2ServerUpgradeCodec(http2Codec);
+            }
+        };
+        http2ConnectionHandler = http2Codec.frameCodec().connectionHandler();
+
+        userEvents = new ArrayList<Object>();
+
+        HttpServerCodec httpServerCodec = new HttpServerCodec();
+        HttpServerUpgradeHandler upgradeHandler = new HttpServerUpgradeHandler(httpServerCodec, upgradeCodecFactory);
+
+        CleartextHttp2ServerUpgradeHandler handler = new CleartextHttp2ServerUpgradeHandler(
+                httpServerCodec, upgradeHandler, http2Codec);
+        channel = new EmbeddedChannel(handler, new ChannelInboundHandlerAdapter() {
+            @Override
+            public void userEventTriggered(ChannelHandlerContext ctx, Object evt) throws Exception {
+                userEvents.add(evt);
+            }
+        });
+
+        assertFalse(channel.writeInbound(Http2CodecUtil.connectionPrefaceBuf()));
+
+        ByteBuf settingsFrame = settingsFrameBuf();
+
+        assertFalse(channel.writeInbound(settingsFrame));
+
+        assertEquals(1, userEvents.size());
+        assertTrue(userEvents.get(0) instanceof PriorKnowledgeUpgradeEvent);
+    }
+
     private static ByteBuf settingsFrameBuf() {
         ByteBuf settingsFrame = Unpooled.buffer();
         settingsFrame.writeMedium(12); // Payload length