Ignore should-scroll-on-main-thread if main frame is not scrollable

Source/core/page/FrameView.cpp

Index: Source/core/page/FrameView.cpp
diff --git a/Source/core/page/FrameView.cpp b/Source/core/page/FrameView.cpp
index 027028cb28c45cdb403d2cf2052e7b6e8053b669..db6cc7b1e48aafd0f0d7c5ce1bb768a1e35a4299 100644
--- a/Source/core/page/FrameView.cpp
+++ b/Source/core/page/FrameView.cpp
@@ -669,7 +669,8 @@ void FrameView::calculateScrollbarModesForLayout(ScrollbarMode& hMode, Scrollbar
                 // It's sufficient to just check the X overflow,
                 // since it's illegal to have visible in only one direction.
                 RenderObject* o = rootRenderer->style()->overflowX() == OVISIBLE && isHTMLHtmlElement(document->documentElement()) ? body->renderer() : rootRenderer;
-                applyOverflowToViewport(o, hMode, vMode);
+                if (o->style())
+                    applyOverflowToViewport(o, hMode, vMode);
             }
         } else if (rootRenderer)
             applyOverflowToViewport(rootRenderer, hMode, vMode);