Allow frames with overflow:hidden scroll in slow scrolling path when scaled up

Source/core/page/FrameView.h

Index: Source/core/page/FrameView.h
diff --git a/Source/core/page/FrameView.h b/Source/core/page/FrameView.h
index ce580f756859471add017eb46db9c2fb48607c57..a4da9aa788669b1a3bf38a033846a7bc3d647ab9 100644
--- a/Source/core/page/FrameView.h
+++ b/Source/core/page/FrameView.h
@@ -87,7 +87,6 @@ public:
     void setMarginHeight(LayoutUnit);
 
     virtual void setCanHaveScrollbars(bool);
-    void updateCanHaveScrollbars();
 
     virtual PassRefPtr<Scrollbar> createScrollbar(ScrollbarOrientation);
 
@@ -268,7 +267,12 @@ public:
 
     bool isScrollable();
 
-    enum ScrollbarModesCalculationStrategy { RulesFromWebContentOnly, AnyRule };
+    enum ScrollbarModesCalculationStrategy {
+        RulesFromWebContent = 1 << 0,
+        RulesFromClient = 1 << 1,
+        RulesFromVisibleContentScaleFactor = 1 << 2,
+        AnyRule = -1,
+    };
     void calculateScrollbarModesForLayout(ScrollbarMode& hMode, ScrollbarMode& vMode, ScrollbarModesCalculationStrategy = AnyRule);
 
     // Normal delay