Add support for Element.getAttributeNames()

third_party/WebKit/Source/core/dom/Element.cpp

Index: third_party/WebKit/Source/core/dom/Element.cpp
diff --git a/third_party/WebKit/Source/core/dom/Element.cpp b/third_party/WebKit/Source/core/dom/Element.cpp
index 9b3b1c9265d311c50dace218d84bd43109089a82..b810a8c377361aa5d8e02fe250db4678c7657e81 100644
--- a/third_party/WebKit/Source/core/dom/Element.cpp
+++ b/third_party/WebKit/Source/core/dom/Element.cpp
@@ -324,6 +324,18 @@ NamedNodeMap* Element::attributesForBindings() const {
   return rare_data.AttributeMap();
 }
 
+Vector<AtomicString> Element::getAttributeNames() const {
+  Vector<AtomicString> attributesVector;
+  if (!hasAttributes())
+    return attributesVector;
+
+  AttributeCollection attributes = element_data_->Attributes();
+  attributesVector.ReserveInitialCapacity(attributes.size());
+  for (const Attribute& attr : attributes)
+    attributesVector.UncheckedAppend(attr.GetName().ToString());
+  return attributesVector;
+}
+
 ElementAnimations* Element::GetElementAnimations() const {
   if (HasRareData())
     return GetElementRareData()->GetElementAnimations();