When the host is unknown, make the HtmlUnitDriver return an error page.

Fixes issue SeleniumHQ#6512.

java/client/src/org/openqa/selenium/htmlunit/HtmlUnitDriver.java

@@ -17,6 +17,8 @@
 
 package org.openqa.selenium.htmlunit;
 
+import static org.openqa.selenium.remote.CapabilityType.SUPPORTS_FINDING_BY_CSS;
+
 import com.google.common.collect.Collections2;
 import com.google.common.collect.ImmutableSet;
 import com.google.common.collect.Maps;
@@ -29,7 +31,9 @@
 import com.gargoylesoftware.htmlunit.ProxyConfig;
 import com.gargoylesoftware.htmlunit.ScriptResult;
 import com.gargoylesoftware.htmlunit.SgmlPage;
+import com.gargoylesoftware.htmlunit.StringWebResponse;
 import com.gargoylesoftware.htmlunit.TopLevelWindow;
+import com.gargoylesoftware.htmlunit.UnexpectedPage;
 import com.gargoylesoftware.htmlunit.WaitingRefreshHandler;
 import com.gargoylesoftware.htmlunit.WebClient;
 import com.gargoylesoftware.htmlunit.WebClientOptions;
@@ -116,8 +120,6 @@
 import java.util.concurrent.Callable;
 import java.util.concurrent.TimeUnit;
 
-import static org.openqa.selenium.remote.CapabilityType.SUPPORTS_FINDING_BY_CSS;
-
 public class HtmlUnitDriver implements WebDriver, JavascriptExecutor,
     FindsById, FindsByLinkText, FindsByXPath, FindsByName, FindsByCssSelector,
     FindsByTagName, FindsByClassName, HasCapabilities, HasInputDevices {
@@ -476,7 +478,10 @@ protected void get(URL fullUrl) {
       // A "get" works over the entire page
       currentWindow = getCurrentWindow().getTopWindow();
     } catch (UnknownHostException e) {
-      // This should be fine
+      getCurrentWindow().getTopWindow().setEnclosedPage(new UnexpectedPage(
+          new StringWebResponse("Unknown host", fullUrl),
+          getCurrentWindow().getTopWindow()
+      ));
     } catch (ConnectException e) {
       // This might be expected
     } catch (SocketTimeoutException e) {

java/client/test/org/openqa/selenium/htmlunit/ErroneousPageLoadingTest.java

@@ -0,0 +1,37 @@
+/*
+Copyright 2014 Selenium committers
+
+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.openqa.selenium.htmlunit;
+
+
+import static org.junit.Assert.assertNotEquals;
+
+import org.junit.Test;
+import org.openqa.selenium.testing.JUnit4TestBase;
+
+public class ErroneousPageLoadingTest extends JUnit4TestBase {
+
+  @Test
+  public void shouldNotReturnSourceOfOldPageWhenLoadFailsDueToABadHost() {
+    driver.get(pages.xhtmlTestPage);
+    String originalSource = driver.getPageSource();
+
+    driver.get("http://thishostdoesnotexist.norshallitever");
+    String currentSource = driver.getPageSource();
+
+    assertNotEquals(originalSource, currentSource);
+  }
+}