Implement option-pop cloning hook in all tree builders

Add necessary corresponding implementations to the other tree builders
that construct persistent trees:

  - DOMTreeBuilder: uses the DOM cloneNode method for deep cloning
  - XOMTreeBuilder: uses XOM’s Node.copy() for deep cloning
  - BrowserTreeBuilder: uses the existing cloneNodeDeep method

Author: sideshowbarker

gwt-src/nu/validator/htmlparser/gwt/BrowserTreeBuilder.java

@@ -474,4 +474,21 @@ private static native void removeChild(JavaScriptObject parent,
             fatal(e);
         }
     }
+
+    @Override
+    protected void cloneOptionContentToSelectedContent(
+            JavaScriptObject option, JavaScriptObject selectedContent)
+            throws SAXException {
+        try {
+            while (hasChildNodes(selectedContent)) {
+                removeChild(selectedContent, getFirstChild(selectedContent));
+            }
+            JavaScriptObject clone = cloneNodeDeep(option);
+            while (hasChildNodes(clone)) {
+                appendChild(selectedContent, getFirstChild(clone));
+            }
+        } catch (JavaScriptException e) {
+            fatal(e);
+        }
+    }
 }

src/nu/validator/htmlparser/dom/DOMTreeBuilder.java

@@ -354,4 +354,21 @@ protected Element createAndInsertFosterParentedElement(String ns, String name,
             fatal(e);
         }
     }
+
+    @Override
+    protected void cloneOptionContentToSelectedContent(Element option,
+            Element selectedContent) throws SAXException {
+        try {
+            while (selectedContent.hasChildNodes()) {
+                selectedContent.removeChild(selectedContent.getFirstChild());
+            }
+            Node child = option.getFirstChild();
+            while (child != null) {
+                selectedContent.appendChild(child.cloneNode(true));
+                child = child.getNextSibling();
+            }
+        } catch (DOMException e) {
+            fatal(e);
+        }
+    }
 }

src/nu/validator/htmlparser/xom/XOMTreeBuilder.java

@@ -348,4 +348,17 @@ private int indexOfTable(Element table, Element stackParent) {
         cachedTableIndex = -1;
         cachedTable = null;
     }
+
+    @Override
+    protected void cloneOptionContentToSelectedContent(Element option,
+            Element selectedContent) throws SAXException {
+        try {
+            selectedContent.removeChildren();
+            for (int i = 0; i < option.getChildCount(); i++) {
+                selectedContent.appendChild(option.getChild(i).copy());
+            }
+        } catch (XMLException e) {
+            fatal(e);
+        }
+    }
 }