HTMLTextAreaElement.defaultValue is not implemented as per spec

Source/core/html/HTMLTextAreaElement.cpp

Index: Source/core/html/HTMLTextAreaElement.cpp
diff --git a/Source/core/html/HTMLTextAreaElement.cpp b/Source/core/html/HTMLTextAreaElement.cpp
index cdf5e58ea41f9c85ccf238c1dedf433dc899722b..8234ff202da06b6a2eecc5a6856784af6ad0fd56 100644
--- a/Source/core/html/HTMLTextAreaElement.cpp
+++ b/Source/core/html/HTMLTextAreaElement.cpp
@@ -413,40 +413,14 @@ void HTMLTextAreaElement::setInnerEditorValue(const String& value)
 
 String HTMLTextAreaElement::defaultValue() const
 {
-    StringBuilder value;
-
-    // Since there may be comments, ignore nodes other than text nodes.
-    for (Node* n = firstChild(); n; n = n->nextSibling()) {
-        if (n->isTextNode())
-            value.append(toText(n)->data());
-    }
-
-    return value.toString();
+    return textContent();
 }
 
 void HTMLTextAreaElement::setDefaultValue(const String& defaultValue)
 {
-    RefPtrWillBeRawPtr<Node> protectFromMutationEvents(this);
-
-    // To preserve comments, remove only the text nodes, then add a single text node.
-    WillBeHeapVector<RefPtrWillBeMember<Node>> textNodes;
-    for (Node* n = firstChild(); n; n = n->nextSibling()) {
-        if (n->isTextNode())
-            textNodes.append(n);
-    }
-    size_t size = textNodes.size();
-    for (size_t i = 0; i < size; ++i)
-        removeChild(textNodes[i].get(), IGNORE_EXCEPTION);
-
-    // Normalize line endings.
-    String value = defaultValue;
-    value.replace("\r\n", "\n");
-    value.replace('\r', '\n');
-
-    insertBefore(document().createTextNode(value), firstChild(), IGNORE_EXCEPTION);
-
+    setTextContent(defaultValue);
     if (!m_isDirty)

[Sunil Ratnu, 2015/07/10 07:47:26]

I tried using ImplementedAs=textContent in the idl as you can see in the
previous patchset but that results into failure of test case
"fast/forms/textarea-selection-preservation.html". The call to setNonDirtyValue
ensures that the textarea selection is preserved. Could you please let me know
if there are any issues with this call being here apart from the call to
setTextContent(). If there are any issues, I will try to come up with some
different approach.

[tkent, 2015/07/10 07:59:40]

Can you add test cases of ta.textContent = '...' to
textarea-selection-preservation.html, similar to existing ta.defaultValue =
'...'?  Do such test cases succeed?

When setTextContent is called, HTMLTextAreaElement::childrenChanged should be
called, then childrenChanged should call setNonDirtyValue.  I wonder why we
still need setNonDirtyValue here.

-        setNonDirtyValue(value);
+        setNonDirtyValue(defaultValue);
 }
 
 int HTMLTextAreaElement::maxLength() const