[root layer scrolls] TopDocumentRootScrollerController needs to use layoutViewportScrollableArea

third_party/WebKit/Source/core/page/scrolling/TopDocumentRootScrollerController.cpp

Index: third_party/WebKit/Source/core/page/scrolling/TopDocumentRootScrollerController.cpp
diff --git a/third_party/WebKit/Source/core/page/scrolling/TopDocumentRootScrollerController.cpp b/third_party/WebKit/Source/core/page/scrolling/TopDocumentRootScrollerController.cpp
index 307aa1a3ed1a717ed6618e6bc8f337f4dd1423eb..45ca262bd519c570d0be834911ef48027c82b2f6 100644
--- a/third_party/WebKit/Source/core/page/scrolling/TopDocumentRootScrollerController.cpp
+++ b/third_party/WebKit/Source/core/page/scrolling/TopDocumentRootScrollerController.cpp
@@ -69,7 +69,11 @@ IntSize TopDocumentRootScrollerController::RootScrollerVisibleArea() const {
       ceilf(page_->GetVisualViewport().BrowserControlsAdjustment() /
             minimum_page_scale);
 
-  return TopDocument()->View()->VisibleContentSize(kExcludeScrollbars) +
+  return TopDocument()
+             ->View()
+             ->LayoutViewportScrollableArea()
+             ->VisibleContentRect(kExcludeScrollbars)
+             .Size() +
          IntSize(0, browser_controls_adjustment);
 }