Extract image URLs in srcset as well

javatests/org/chromium/distiller/webdocument/WebImageTest.java

+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package org.chromium.distiller.webdocument;
+
+import org.chromium.distiller.DomDistillerJsTestCase;
+
+import java.util.List;
+
+import com.google.gwt.dom.client.Document;
+import com.google.gwt.dom.client.ImageElement;
+
+public class WebImageTest extends DomDistillerJsTestCase {
+    public void testGetSrcList() {
+        ImageElement img = Document.get().createImageElement();
+        img.setSrc("http://example.com/image");
+        img.setAttribute("srcset",
+                "http://example.com/image200 200w, http://example.com/image400 400w");
+        WebImage wi = new WebImage(img, 1, 1, img.getSrc());
+        List<String> urls = wi.getUrlList();
+        assertEquals(3, urls.size());
+        assertEquals("http://example.com/image", urls.get(0));
+        assertEquals("http://example.com/image200", urls.get(1));
+        assertEquals("http://example.com/image400", urls.get(2));
+    }
+}