Oilpan: make ViewportAnchor fully stack allocated.

Source/web/ViewportAnchor.h

Index: Source/web/ViewportAnchor.h
diff --git a/Source/web/ViewportAnchor.h b/Source/web/ViewportAnchor.h
index 6348e0fa621f64838d0f43fbe41ee4e595c9cf7f..47167e657b9808c88491f23d51f0c7ddd51c36e6 100644
--- a/Source/web/ViewportAnchor.h
+++ b/Source/web/ViewportAnchor.h
@@ -54,7 +54,7 @@ namespace blink {
 // its orientation relative to the node, and the viewport origin maintains its
 // orientation relative to the anchor.
 class ViewportAnchor {
-    WTF_MAKE_NONCOPYABLE(ViewportAnchor);
+    STACK_ALLOCATED();
 public:
     explicit ViewportAnchor(WebCore::EventHandler* eventHandler);
 
@@ -63,11 +63,11 @@ public:
     WebCore::IntPoint computeOrigin(const WebCore::IntSize& currentViewSize) const;
 
 private:
-    WebCore::EventHandler* m_eventHandler;
+    RawPtrWillBeMember<WebCore::EventHandler> m_eventHandler;
 
     WebCore::IntRect m_viewRect;
 
-    RefPtrWillBePersistent<WebCore::Node> m_anchorNode;
+    RefPtrWillBeMember<WebCore::Node> m_anchorNode;
     WebCore::LayoutRect m_anchorNodeBounds;
 
     WebCore::FloatSize m_anchorInViewCoords;