Adding FX WebView based sample to demonstrate the performance when running on top of HotSpot VM. Use following command to try:

teavm-samples/teavm-samples-benchmark$ mvn clean install && mvn -Pfx exec:java

teavm-samples/teavm-samples-benchmark/pom.xml

@@ -76,6 +76,11 @@
       <artifactId>html5-canvas</artifactId>
       <version>0.7.1</version>
     </dependency>
+    <dependency>
+      <groupId>org.netbeans.html</groupId>
+      <artifactId>net.java.html.boot</artifactId>
+      <version>1.1</version>
+    </dependency>
   </dependencies>
 
   <build>
@@ -194,10 +199,47 @@
         <groupId>org.apache.maven.plugins</groupId>
         <artifactId>maven-source-plugin</artifactId>
       </plugin>
+      <plugin>
+        <groupId>org.netbeans.html</groupId>
+        <artifactId>html4j-maven-plugin</artifactId>
+        <version>1.1</version>
+        <executions>
+            <execution>
+                <goals>
+                    <goal>process-js-annotations</goal>
+                </goals>
+            </execution>
+        </executions>
+      </plugin>
       <plugin>
         <groupId>org.apache.maven.plugins</groupId>
         <artifactId>maven-javadoc-plugin</artifactId>
       </plugin>
     </plugins>
   </build>
+  <profiles>
+      <profile>
+          <id>fx</id>
+          <dependencies>
+              <dependency>
+                  <groupId>org.netbeans.html</groupId>
+                  <artifactId>net.java.html.boot.fx</artifactId>
+                  <version>1.1</version>
+                  <scope>runtime</scope>
+              </dependency>
+          </dependencies>
+          <build>
+              <plugins>
+                  <plugin>
+                      <groupId>org.codehaus.mojo</groupId>
+                      <artifactId>exec-maven-plugin</artifactId>
+                      <version>1.3.2</version>
+                      <configuration>
+                          <mainClass>org.teavm.samples.benchmark.bck2brwsr.BenchmarkFX</mainClass>
+                      </configuration>
+                  </plugin>
+              </plugins>
+          </build>
+      </profile>
+  </profiles>
 </project>

teavm-samples/teavm-samples-benchmark/src/main/java/org/teavm/samples/benchmark/bck2brwsr/BenchmarkFX.java

@@ -0,0 +1,29 @@
+/*
+ * Copyright 2015 jarda.
+ *
+ * Licensed 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 org.teavm.samples.benchmark.bck2brwsr;
+
+import net.java.html.boot.BrowserBuilder;
+
+public class BenchmarkFX {
+    public static void main(String... args) {
+        BrowserBuilder.newBrowser().loadPage("fx.html")
+            .loadClass(BenchmarkStarter.class)
+            .invoke("main")
+            .showAndWait();
+        System.exit(0);
+    }
+    
+}

teavm-samples/teavm-samples-benchmark/src/main/java/org/teavm/samples/benchmark/bck2brwsr/BenchmarkStarter.java

@@ -20,6 +20,8 @@ import com.dukescript.api.canvas.Style;
 import com.dukescript.canvas.html.HTML5Graphics;
 import java.util.Timer;
 import java.util.TimerTask;
+import net.java.html.BrwsrCtx;
+import net.java.html.js.JavaScriptBody;
 import org.jbox2d.collision.shapes.CircleShape;
 import org.jbox2d.collision.shapes.PolygonShape;
 import org.jbox2d.collision.shapes.Shape;
@@ -35,28 +37,30 @@ public class BenchmarkStarter {
     private static double startMillisecond;
     private static int currentSecond;
     private static double timeSpentCalculating;
+    private static BrwsrCtx ctx;
     
     public static void main(String[] args) {
         startMillisecond = System.currentTimeMillis();
+        ctx = BrwsrCtx.findDefault(BenchmarkStarter.class);
         makeStep();
     }
+    
+    static void makeStep() {
+        ctx.execute(new Runnable() {
+            @Override
+            public void run() {
+                makeStep0();
+            }
+        });
+    }
 
-    private static void makeStep() {
+    private static void makeStep0() {
         double start = System.currentTimeMillis();
         scene.calculate();
         double end = System.currentTimeMillis();
         int second = (int)((System.currentTimeMillis() - startMillisecond) / 1000);
         if (second > currentSecond) {
-            /*
+            publishResults(second, timeSpentCalculating);
-            HTMLElement row = document.createElement("tr");
-            resultTableBody.appendChild(row);
-            HTMLElement secondCell = document.createElement("td");
-            row.appendChild(secondCell);
-            secondCell.appendChild(document.createTextNode(String.valueOf(second)));
-            HTMLElement timeCell = document.createElement("td");
-            row.appendChild(timeCell);
-            timeCell.appendChild(document.createTextNode(String.valueOf(timeSpentCalculating)));
-*/
             timeSpentCalculating = 0;
             currentSecond = second;
         }
@@ -109,4 +113,17 @@ public class BenchmarkStarter {
         }
         context.restore();
     }
+    
+    @JavaScriptBody(args = { "second", "timeSpentCalculating" }, body = 
+        "var resultTableBody = document.getElementById('result-table-body');\n" +
+        "var row = document.createElement(\"tr\");\n" +
+        "resultTableBody.appendChild(row);\n" +
+        "var secondCell = document.createElement(\"td\");\n" +
+        "row.appendChild(secondCell);\n" +
+        "secondCell.appendChild(document.createTextNode(second));\n" +
+        "var timeCell = document.createElement(\"td\");\n" +
+        "row.appendChild(timeCell);\n" +
+        "timeCell.appendChild(document.createTextNode(timeSpentCalculating));\n"
+    )
+    private static native void publishResults(int second, double time);
 }

teavm-samples/teavm-samples-benchmark/src/main/resources/org/teavm/samples/benchmark/bck2brwsr/fx.html

@@ -0,0 +1,37 @@
+<!--
+    Copyright 2014 Alexey Andreev.
+
+    Licensed 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.
+-->
+<!DOCTYPE html>
+<html>
+  <head>
+    <meta http-equiv="Content-Type" content="text/html;charset=utf-8">
+    <title>HotSpot/JavaFX jbox2d benchmark</title>
+  </head>
+  <body>
+    <h1>HotSpot/JavaFX performance</h1>
+    <div>
+      <canvas id="benchmark-canvas" width="600" height="600"></canvas>
+    </div>
+    <table>
+      <thead>
+        <tr>
+          <th>Second</th>
+          <th>Time spent computing, ms</th>
+        </tr>
+      </thead>
+      <tbody id="result-table-body">
+      </tbody>
+    </table>
+</html>