Revert of Remove FrameView::Root

third_party/WebKit/Source/core/frame/FrameView.cpp

 /*
  * Copyright (C) 1998, 1999 Torben Weis <weis@kde.org>
  *                     1999 Lars Knoll <knoll@kde.org>
  *                     1999 Antti Koivisto <koivisto@kde.org>
  *                     2000 Dirk Mueller <mueller@kde.org>
  * Copyright (C) 2004, 2005, 2006, 2007, 2008 Apple Inc. All rights reserved.
  *           (C) 2006 Graham Dennis (graham.dennis@gmail.com)
  *           (C) 2006 Alexey Proskuryakov (ap@nypop.com)
  * Copyright (C) 2009 Google Inc. All rights reserved.
  *
@@ skipping 3831 matching lines @@
     animating_scrollable_areas_ = new ScrollableAreaSet;
   animating_scrollable_areas_->insert(scrollable_area);
 }
 
 void FrameView::RemoveAnimatingScrollableArea(ScrollableArea* scrollable_area) {
   if (!animating_scrollable_areas_)
     return;
   animating_scrollable_areas_->erase(scrollable_area);
 }
 
+FrameView* FrameView::Root() const {
+  const FrameView* top = this;
+  while (top->Parent())
+    top = ToFrameView(top->Parent());
+  return const_cast<FrameView*>(top);
+}
+
 void FrameView::SetParent(FrameViewBase* parent_frame_view_base) {
   FrameView* parent = ToFrameView(parent_frame_view_base);
   if (parent == parent_)
     return;
 
   DCHECK(!parent || !parent_);
   if (!parent || !parent->IsVisible())
     SetParentVisible(false);
   parent_ = parent;
   if (parent && parent->IsVisible())
@@ skipping 1525 matching lines @@
 void FrameView::SetAnimationHost(
     std::unique_ptr<CompositorAnimationHost> host) {
   animation_host_ = std::move(host);
 }
 
 LayoutUnit FrameView::CaretWidth() const {
   return LayoutUnit(GetChromeClient()->WindowToViewportScalar(1));
 }
 
 }  // namespace blink