Remove unused shouldOnlyIncludeDirectChildren

It seems this one is no longer needed, just
the one in HTMLCollection is used.

Review URL: https://codereview.chromium.org/461213002

git-svn-id: svn://svn.chromium.org/blink/trunk@180131 bbb929c8-8fbe-4397-9dbb-9b2b20218538

third_party/WebKit/Source/core/dom/LiveNodeList.h

@@ -48,8 +48,6 @@ public:
     virtual void invalidateCache(Document* oldDocument = 0) const OVERRIDE FINAL;
     void invalidateCacheForAttribute(const QualifiedName*) const;
 
-    bool shouldOnlyIncludeDirectChildren() const { return false; }
-
     // Collection IndexCache API.
     bool canTraverseBackward() const { return true; }
     Element* traverseToFirstElement() const;