WIP (Introduce WTF::NonNullPtr<T>.)

Source/core/html/FormAssociatedElement.cpp

Index: Source/core/html/FormAssociatedElement.cpp
diff --git a/Source/core/html/FormAssociatedElement.cpp b/Source/core/html/FormAssociatedElement.cpp
index e800826d4fb7ac47a934c4b5717ec454268ce4c8..4ef42ffe0cbbf8f79b38caaab9ad6ee173ed38ea 100644
--- a/Source/core/html/FormAssociatedElement.cpp
+++ b/Source/core/html/FormAssociatedElement.cpp
@@ -107,7 +107,7 @@ HTMLFormElement* FormAssociatedElement::findAssociatedForm(const HTMLElement* el
         // the value of form attribute, so we put the result of
         // treeScope()->getElementById() over the given element.
         HTMLFormElement* newForm = 0;
-        Element* newFormCandidate = element->treeScope().getElementById(formId);
+        Element* newFormCandidate = element->treeScope()->getElementById(formId);
         if (newFormCandidate && newFormCandidate->hasTagName(formTag))
             newForm = toHTMLFormElement(newFormCandidate);
         return newForm;
@@ -293,7 +293,7 @@ PassOwnPtr<FormAttributeTargetObserver> FormAttributeTargetObserver::create(cons
 }
 
 FormAttributeTargetObserver::FormAttributeTargetObserver(const AtomicString& id, FormAssociatedElement* element)
-    : IdTargetObserver(toHTMLElement(element)->treeScope().idTargetObserverRegistry(), id)
+    : IdTargetObserver(toHTMLElement(element)->treeScope()->idTargetObserverRegistry(), id)
     , m_element(element)
 {
 }