Implement cloneNode for Document

Source/core/dom/Document.cpp

Index: Source/core/dom/Document.cpp
diff --git a/Source/core/dom/Document.cpp b/Source/core/dom/Document.cpp
index 3a9216003d3c4c679c0e648ce5703314be7db56b..3a37618ee68bc1ad58126b20aa223970df8009e4 100644
--- a/Source/core/dom/Document.cpp
+++ b/Source/core/dom/Document.cpp
@@ -3090,11 +3090,30 @@ bool Document::canReplaceChild(Node* newChild, Node* oldChild)
     return true;
 }
 
-PassRefPtr<Node> Document::cloneNode(bool /*deep*/)
+PassRefPtr<Node> Document::cloneNode(bool deep)
 {
-    // Spec says cloning Document nodes is "implementation dependent"
-    // so we do not support it...
-    return 0;
+    RefPtr<Document> clone = cloneDocumentWithoutChildren();
+    clone->cloneDataFromDocument(*this);
+    if (deep)
+        cloneChildNodes(clone.get());
+    return clone.release();
+}
+
+PassRefPtr<Document> Document::cloneDocumentWithoutChildren()
+{
+    DocumentInit init(url());
+    if (isXHTMLDocument())
+        return createXHTML(init.withRegistrationContext(registrationContext()));
+    return create(init);
+}
+
+void Document::cloneDataFromDocument(const Document& other)
+{
+    setCompatibilityMode(other.compatibilityMode());
+    setSecurityOrigin(other.securityOrigin());

[abarth-chromium, 2013/08/26 21:04:55]

You should make a copy of the security origin.  The security origin object is
mutable, which means mutations will affect both documents.

+    setContextFeatures(other.contextFeatures());
+
+    setDecoder(TextResourceDecoder::create(other.suggestedMIMEType(), other.encoding()));

[abarth-chromium, 2013/08/26 21:04:55]

This doesn't make a lot of sense...  There is no text resource to decode.

jamesr is in the process of removing the TextResourceDecoder member from
Document, which will make this easier.

What about the HTMLImports state?  How do we decide which state to clone here?

[jamesr, 2013/08/26 21:07:51]

Have you tested that the exposed encoding on the new document should match the
old one?  If so, then we just need to call setEncoding(other.encoding()) once
https://codereview.chromium.org/22909053/ lands.  I'm not sure that makes sense,
though, since the cloned document wasn't generated by decoding an encoded
resource.

 }
 
 StyleSheetList* Document::styleSheets()