Oilpan: make DocumentFragment a heap allocated object.

Source/core/dom/Document.cpp

Index: Source/core/dom/Document.cpp
diff --git a/Source/core/dom/Document.cpp b/Source/core/dom/Document.cpp
index 090a67584cdb9ab6d60ef8100eccc794d8a3d452..de0374728dd7119f21aaec7b2325b689a5f16edb 100644
--- a/Source/core/dom/Document.cpp
+++ b/Source/core/dom/Document.cpp
@@ -863,7 +863,7 @@ LocalFrame* Document::executingFrame()
     return window->frame();
 }
 
-PassRefPtr<DocumentFragment> Document::createDocumentFragment()
+PassRefPtrWillBeRawPtr<DocumentFragment> Document::createDocumentFragment()
 {
     return DocumentFragment::create(*this);
 }
@@ -981,7 +981,7 @@ PassRefPtr<Node> Document::importNode(Node* importedNode, bool deep, ExceptionSt
             return nullptr;
         }
         DocumentFragment* oldFragment = toDocumentFragment(importedNode);
-        RefPtr<DocumentFragment> newFragment = createDocumentFragment();
+        RefPtrWillBeRawPtr<DocumentFragment> newFragment = createDocumentFragment();
         if (deep && !importContainerNodeChildren(oldFragment, newFragment, exceptionState))
             return nullptr;