Add HttpObjectEncoderBenchmark

Motivation:
Benchmark to measure HttpObjectEncoder performance.

Modifications:
- Create new benchmark HttpObjectEncoderBenchmark

Result:
JMH Microbenchmark for HttpObjectEncoder.

microbench/src/main/java/io/netty/microbench/http/HttpObjectEncoderBenchmark.java

@@ -0,0 +1,126 @@
+/*
+ * Copyright 2016 The Netty Project
+ *
+ * The Netty Project licenses this file to you under the Apache License,
+ * version 2.0 (the "License"); you may not use this file except in compliance
+ * with the License. You may obtain a copy of the License at:
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations
+ * under the License.
+ */
+package io.netty.microbench.http;
+
+import io.netty.buffer.ByteBuf;
+import io.netty.buffer.PooledByteBufAllocator;
+import io.netty.buffer.Unpooled;
+import io.netty.buffer.UnpooledByteBufAllocator;
+import io.netty.channel.ChannelHandlerContext;
+import io.netty.channel.ChannelPromise;
+import io.netty.handler.codec.http.DefaultFullHttpRequest;
+import io.netty.handler.codec.http.DefaultHttpHeaders;
+import io.netty.handler.codec.http.DefaultHttpRequest;
+import io.netty.handler.codec.http.DefaultLastHttpContent;
+import io.netty.handler.codec.http.EmptyHttpHeaders;
+import io.netty.handler.codec.http.FullHttpRequest;
+import io.netty.handler.codec.http.HttpHeaderNames;
+import io.netty.handler.codec.http.HttpHeaderValues;
+import io.netty.handler.codec.http.HttpHeaders;
+import io.netty.handler.codec.http.HttpMethod;
+import io.netty.handler.codec.http.HttpRequest;
+import io.netty.handler.codec.http.HttpRequestEncoder;
+import io.netty.handler.codec.http.HttpVersion;
+import io.netty.handler.codec.http.LastHttpContent;
+import io.netty.microbench.channel.EmbeddedChannelWriteReleaseHandlerContext;
+import io.netty.microbench.util.AbstractMicrobenchmark;
+import org.openjdk.jmh.annotations.Benchmark;
+import org.openjdk.jmh.annotations.Fork;
+import org.openjdk.jmh.annotations.Level;
+import org.openjdk.jmh.annotations.Measurement;
+import org.openjdk.jmh.annotations.Param;
+import org.openjdk.jmh.annotations.Scope;
+import org.openjdk.jmh.annotations.Setup;
+import org.openjdk.jmh.annotations.State;
+import org.openjdk.jmh.annotations.TearDown;
+import org.openjdk.jmh.annotations.Threads;
+import org.openjdk.jmh.annotations.Warmup;
+
+@State(Scope.Benchmark)
+@Fork(1)
+@Threads(1)
+@Warmup(iterations = 5)
+@Measurement(iterations = 10)
+public class HttpObjectEncoderBenchmark extends AbstractMicrobenchmark {
+    private HttpRequestEncoder encoder;
+    private FullHttpRequest fullRequest;
+    private LastHttpContent lastContent;
+    private HttpRequest contentLengthRequest;
+    private HttpRequest chunkedRequest;
+    private ByteBuf content;
+    private ChannelHandlerContext context;
+
+    @Param({ "true", "false" })
+    public boolean pooledAllocator;
+
+    @Param({ "true", "false" })
+    public boolean voidPromise;
+
+    @Setup(Level.Trial)
+    public void setup() {
+        byte[] bytes = new byte[256];
+        content = Unpooled.buffer(bytes.length);
+        content.writeBytes(bytes);
+        ByteBuf testContent = Unpooled.unreleasableBuffer(content.asReadOnly());
+        HttpHeaders headersWithChunked = new DefaultHttpHeaders(false);
+        headersWithChunked.add(HttpHeaderNames.TRANSFER_ENCODING, HttpHeaderValues.CHUNKED);
+        HttpHeaders headersWithContentLength = new DefaultHttpHeaders(false);
+        headersWithContentLength.add(HttpHeaderNames.CONTENT_LENGTH, testContent.readableBytes());
+
+        fullRequest = new DefaultFullHttpRequest(HttpVersion.HTTP_1_1, HttpMethod.POST, "/index", testContent,
+                headersWithContentLength, EmptyHttpHeaders.INSTANCE);
+        contentLengthRequest = new DefaultHttpRequest(HttpVersion.HTTP_1_1, HttpMethod.POST, "/index",
+                headersWithContentLength);
+        chunkedRequest = new DefaultHttpRequest(HttpVersion.HTTP_1_1, HttpMethod.POST, "/index", headersWithChunked);
+        lastContent = new DefaultLastHttpContent(testContent, false);
+
+        encoder = new HttpRequestEncoder();
+        context = new EmbeddedChannelWriteReleaseHandlerContext(pooledAllocator ? PooledByteBufAllocator.DEFAULT :
+                UnpooledByteBufAllocator.DEFAULT, encoder) {
+            @Override
+            protected void handleException(Throwable t) {
+                handleUnexpectedException(t);
+            }
+        };
+    }
+
+    @TearDown(Level.Trial)
+    public void teardown() {
+        content.release();
+        content = null;
+    }
+
+    @Benchmark
+    public void fullMessage() throws Exception {
+        encoder.write(context, fullRequest, newPromise());
+    }
+
+    @Benchmark
+    public void contentLength() throws Exception {
+        encoder.write(context, contentLengthRequest, newPromise());
+        encoder.write(context, lastContent, newPromise());
+    }
+
+    @Benchmark
+    public void chunked() throws Exception {
+        encoder.write(context, chunkedRequest, newPromise());
+        encoder.write(context, lastContent, newPromise());
+    }
+
+    private ChannelPromise newPromise() {
+        return voidPromise ? context.voidPromise() : context.newPromise();
+    }
+}