Add fast path for tag#id selector queries

Source/core/dom/TreeScope.cpp

Index: Source/core/dom/TreeScope.cpp
diff --git a/Source/core/dom/TreeScope.cpp b/Source/core/dom/TreeScope.cpp
index 3e0494c950cca921f54a5a229db8d9b093f2b840..8f67df1807e058057398af7aa0edf32736520502 100644
--- a/Source/core/dom/TreeScope.cpp
+++ b/Source/core/dom/TreeScope.cpp
@@ -150,6 +150,15 @@ Element* TreeScope::getElementById(const AtomicString& elementId) const
     return m_elementsById->getElementById(elementId.impl(), this);
 }
 
+const Vector<Element*>* TreeScope::getAllElementsById(const AtomicString& elementId) const
+{
+    if (elementId.isEmpty())
+        return 0;
+    if (!m_elementsById)
+        return 0;

[esprehn, 2013/12/17 18:57:48]

Why not return emptyVector? We should just add a static local I think.

[Inactive, 2013/12/17 21:20:24]

Done.

+    return m_elementsById->getAllElementsById(elementId.impl(), this);
+}
+
 void TreeScope::addElementById(const AtomicString& elementId, Element* element)
 {
     if (!m_elementsById)