[RLS] Update iframe scrollbar behaviour based on scrolling attribute

third_party/WebKit/Source/core/paint/PaintLayerScrollableArea.cpp

 /*
  * Copyright (C) 2006, 2007, 2008, 2009, 2010, 2011, 2012 Apple Inc. All rights
  * reserved.
  *
  * Portions are Copyright (C) 1998 Netscape Communications Corporation.
  *
  * Other contributors:
  *   Robert O'Callahan <roc+@cs.cmu.edu>
  *   David Baron <dbaron@fas.harvard.edu>
  *   Christian Biesinger <cbiesinger@gmail.com>
@@ skipping 627 matching lines @@
     if (FrameView* frame_view = frame->View())
       frame_view->RemoveAnimatingScrollableArea(this);
   }
 }
 
 bool PaintLayerScrollableArea::UserInputScrollable(
     ScrollbarOrientation orientation) const {
   if (Box().IsIntrinsicallyScrollable(orientation))
     return true;
 
+  if (Box().IsLayoutView()) {
+    if (LocalFrame* frame = Box().GetFrame()) {
+      if (FrameView* frame_view = frame->View()) {
+        ScrollbarMode h_mode;
+        ScrollbarMode v_mode;
+        frame_view->CalculateScrollbarModes(h_mode, v_mode);
+        if (orientation == kHorizontalScrollbar &&
+            h_mode == kScrollbarAlwaysOff)
+          return false;
+        if (orientation == kVerticalScrollbar && v_mode == kScrollbarAlwaysOff)
+          return false;
+      }
+    }
+  }
+
   EOverflow overflow_style = (orientation == kHorizontalScrollbar)
                                  ? Box().Style()->OverflowX()
                                  : Box().Style()->OverflowY();
   return (overflow_style == EOverflow::kScroll ||
           overflow_style == EOverflow::kAuto ||
           overflow_style == EOverflow::kOverlay);
 }
 
 bool PaintLayerScrollableArea::ShouldPlaceVerticalScrollbarOnLeft() const {
   return Box().ShouldPlaceBlockDirectionScrollbarOnLogicalLeft();
@@ skipping 590 matching lines @@
   // values, due to which we are destroying the scrollbars that were already
   // present.
   if (Box().IsLayoutView()) {
     if (LocalFrame* frame = Box().GetFrame()) {
       if (FrameView* frame_view = frame->View()) {
         ScrollbarMode h_mode;
         ScrollbarMode v_mode;
         frame_view->CalculateScrollbarModes(h_mode, v_mode);
         if (h_mode == kScrollbarAlwaysOn)
           needs_horizontal_scrollbar = true;
+        else if (h_mode == kScrollbarAlwaysOff)
+          needs_horizontal_scrollbar = false;
         if (v_mode == kScrollbarAlwaysOn)
           needs_vertical_scrollbar = true;
+        else if (v_mode == kScrollbarAlwaysOff)
+          needs_vertical_scrollbar = false;
       }
     }
   }
 }
 
 bool PaintLayerScrollableArea::SetHasHorizontalScrollbar(bool has_scrollbar) {
   if (FreezeScrollbarsScope::ScrollbarsAreFrozen())
     return false;
 
   if (has_scrollbar == HasHorizontalScrollbar())
@@ skipping 454 matching lines @@
   LocalFrame* frame = Box().GetFrame();
   if (!frame)
     return;
 
   FrameView* frame_view = frame->View();
   if (!frame_view)
     return;
 
   bool is_visible_to_hit_test = Box().Style()->VisibleToHitTesting();
   bool did_scroll_overflow = scrolls_overflow_;
+  if (Box().IsLayoutView()) {
+    ScrollbarMode h_mode;
+    ScrollbarMode v_mode;
+    frame_view->CalculateScrollbarModes(h_mode, v_mode);
+    if (h_mode == kScrollbarAlwaysOff && v_mode == kScrollbarAlwaysOff)
+      has_overflow = false;
+  }
   scrolls_overflow_ = has_overflow && is_visible_to_hit_test;
   if (did_scroll_overflow == ScrollsOverflow())
     return;
 
   if (RuntimeEnabledFeatures::slimmingPaintInvalidationEnabled()) {
     // The scroll and scroll offset properties depend on |scrollsOverflow| (see:
     // PaintPropertyTreeBuilder::updateScrollAndScrollTranslation).
     Box().SetNeedsPaintPropertyUpdate();
   }
 
@@ skipping 393 matching lines @@
 
 void PaintLayerScrollableArea::DelayScrollOffsetClampScope::
     ClampScrollableAreas() {
   for (auto& scrollable_area : *needs_clamp_)
     scrollable_area->ClampScrollOffsetAfterOverflowChange();
   delete needs_clamp_;
   needs_clamp_ = nullptr;
 }
 
 }  // namespace blink