Add a way to override browser factory

Use the parameter browser.factory to select a class implementing
TestBenchBrowserFactory.

Change-Id: Ibc1f11ad83f8ac1ed85766892cfa0463af9bf440

uitest/src/test/java/com/vaadin/tests/tb3/VaadinBrowserFactory.java

@@ -15,17 +15,44 @@
  */
 package com.vaadin.tests.tb3;
 
+import java.util.logging.Logger;
+
 import org.openqa.selenium.Platform;
 import org.openqa.selenium.ie.InternetExplorerDriver;
 import org.openqa.selenium.remote.DesiredCapabilities;
 
 import com.vaadin.testbench.parallel.Browser;
 import com.vaadin.testbench.parallel.DefaultBrowserFactory;
+import com.vaadin.testbench.parallel.TestBenchBrowserFactory;
 
 public class VaadinBrowserFactory extends DefaultBrowserFactory {
 
+	TestBenchBrowserFactory delegate = null;
+
     @Override
     public DesiredCapabilities create(Browser browser) {
+        String browserFactoryClass = System.getProperty("browser.factory");
+        if (browserFactoryClass != null
+                && !browserFactoryClass.trim().isEmpty()) {
+            if (delegate == null) {
+                getLogger()
+                        .info("Using browser factory " + browserFactoryClass);
+                try {
+                    delegate = (TestBenchBrowserFactory) getClass()
+                            .getClassLoader().loadClass(browserFactoryClass)
+                            .newInstance();
+                } catch (Exception e) {
+                    getLogger().warning("Failed to instantiate browser factory " + browserFactoryClass);
+                    throw new RuntimeException(e);
+                }
+            }
+            return delegate.create(browser);
+        }
+
+    	return doCreate(browser);
+    }
+
+    public DesiredCapabilities doCreate(Browser browser) {
         switch (browser) {
         case IE8:
             return createIE(browser, "8");
@@ -59,4 +86,8 @@ public DesiredCapabilities create(Browser browser, String version) {
         capabilities.setVersion(version);
         return capabilities;
     }
+
+    private static final Logger getLogger() {
+        return Logger.getLogger(VaadinBrowserFactory.class.getName());
+    }
 }