[Layout API] Add LocalFrame::contentLayoutItem and use in VisualViewport

third_party/WebKit/Source/core/frame/LocalFrame.h

Index: third_party/WebKit/Source/core/frame/LocalFrame.h
diff --git a/third_party/WebKit/Source/core/frame/LocalFrame.h b/third_party/WebKit/Source/core/frame/LocalFrame.h
index 54921de18f718f9eb5b0d15b15b6506cf7cccc34..4e488c8ee9a5ec43c06d36b8f93532431eff1613 100644
--- a/third_party/WebKit/Source/core/frame/LocalFrame.h
+++ b/third_party/WebKit/Source/core/frame/LocalFrame.h
@@ -62,6 +62,7 @@ class InputMethodController;
 class IntPoint;
 class IntSize;
 class InstrumentingAgents;
+class LayoutViewItem;
 class LocalDOMWindow;
 class NavigationScheduler;
 class Node;
@@ -112,6 +113,7 @@ public:
     Element* pagePopupOwner() const { return m_pagePopupOwner.get(); }
 
     LayoutView* contentLayoutObject() const; // Root of the layout tree for the document contained in this frame.
+    LayoutViewItem contentLayoutItem() const;
 
     Editor& editor() const;
     EventHandler& eventHandler() const;