Use hasRareData() rather than null-checking elementRareData().

R=eae@chromium.org,atotic@chromium.org
BUG=

Review-Url: https://codereview.chromium.org/2010683002
Cr-Commit-Position: refs/heads/master@{#397851}

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

@@ -2615,7 +2615,7 @@ Node* Element::insertAdjacent(const String& where, Node* newChild, ExceptionStat
 
 NodeIntersectionObserverData* Element::intersectionObserverData() const
 {
-    if (elementRareData())
+    if (hasRareData())
         return elementRareData()->intersectionObserverData();
     return nullptr;
 }