Avoid calling hasAttribute() and then getAttribute() for performance

Source/core/editing/SplitElementCommand.cpp

Index: Source/core/editing/SplitElementCommand.cpp
diff --git a/Source/core/editing/SplitElementCommand.cpp b/Source/core/editing/SplitElementCommand.cpp
index 128c37097edf83107af7d220dc03e76eaf48d020..02a2761812444d0cca8f7c7ecac733923fd87042 100644
--- a/Source/core/editing/SplitElementCommand.cpp
+++ b/Source/core/editing/SplitElementCommand.cpp
@@ -93,8 +93,9 @@ void SplitElementCommand::doUnapply()
         m_element2->insertBefore(children[i].get(), refChild.get(), IGNORE_EXCEPTION);
 
     // Recover the id attribute of the original element.
-    if (m_element1->hasAttribute(HTMLNames::idAttr))
-        m_element2->setAttribute(HTMLNames::idAttr, m_element1->getAttribute(HTMLNames::idAttr));
+    const AtomicString& id = m_element1->getAttribute(HTMLNames::idAttr);
+    if (!id.isNull())
+        m_element2->setAttribute(HTMLNames::idAttr, id);
 
     m_element1->remove(IGNORE_EXCEPTION);
 }