Implement Element.scrollIntoView for scroll-behavior: smooth.

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 191 matching lines @@
   visitor->Trace(scroll_anchor_);
   ScrollableArea::Trace(visitor);
 }
 
 PlatformChromeClient* PaintLayerScrollableArea::GetChromeClient() const {
   if (Page* page = Box().GetFrame()->GetPage())
     return &page->GetChromeClient();
   return nullptr;
 }
 
+SmoothScrollSequencer* PaintLayerScrollableArea::GetSmoothScrollSequencer()
+    const {
+  if (Page* page = Box().GetFrame()->GetPage())
+    return page->GetSmoothScrollSequencer();
+  return nullptr;
+}
+
 GraphicsLayer* PaintLayerScrollableArea::LayerForScrolling() const {
   return Layer()->HasCompositedLayerMapping()
              ? Layer()->GetCompositedLayerMapping()->ScrollingContentsLayer()
              : 0;
 }
 
 GraphicsLayer* PaintLayerScrollableArea::LayerForHorizontalScrollbar() const {
   // See crbug.com/343132.
   DisableCompositingQueryAsserts disabler;
 
@@ skipping 1510 matching lines @@
   document.UpdateStyleAndLayout();
 
   // FIXME (Radar 4118564): We should also autoscroll the window as necessary to
   // keep the point under the cursor in view.
 }
 
 LayoutRect PaintLayerScrollableArea::ScrollIntoView(
     const LayoutRect& rect,
     const ScrollAlignment& align_x,
     const ScrollAlignment& align_y,
+    bool is_smooth,
     ScrollType scroll_type) {
   LayoutRect local_expose_rect(
       Box()
           .AbsoluteToLocalQuad(FloatQuad(FloatRect(rect)), kUseTransforms)
           .BoundingBox());
   local_expose_rect.Move(-Box().BorderLeft(), -Box().BorderTop());
   LayoutRect visible_rect(LayoutPoint(), ClientSize());
   LayoutRect r = ScrollAlignment::GetRectToExpose(
       visible_rect, local_expose_rect, align_x, align_y);
 
   ScrollOffset old_scroll_offset = GetScrollOffset();
   ScrollOffset new_scroll_offset(ClampScrollOffset(RoundedIntSize(
       ToScrollOffset(FloatPoint(r.Location()) + old_scroll_offset))));
-  SetScrollOffset(new_scroll_offset, scroll_type, kScrollBehaviorInstant);
-  ScrollOffset scroll_offset_difference = GetScrollOffset() - old_scroll_offset;
+  if (is_smooth) {
+    DCHECK(scroll_type == kProgrammaticScroll);
+    GetSmoothScrollSequencer()->QueueAnimation(this, new_scroll_offset);
+  } else {
+    SetScrollOffset(new_scroll_offset, scroll_type, kScrollBehaviorInstant);
+  }
+  ScrollOffset scroll_offset_difference =
+      ClampScrollOffset(new_scroll_offset) - old_scroll_offset;
   local_expose_rect.Move(-LayoutSize(scroll_offset_difference));
 
   LayoutRect intersect =
       LocalToAbsolute(Box(), Intersection(visible_rect, local_expose_rect));
   if (intersect.IsEmpty() && !visible_rect.IsEmpty() &&
       !local_expose_rect.IsEmpty()) {
     return LocalToAbsolute(Box(), local_expose_rect);
   }
   return intersect;
 }
@@ skipping 426 matching lines @@
 
 void PaintLayerScrollableArea::DelayScrollOffsetClampScope::
     ClampScrollableAreas() {
   for (auto& scrollable_area : *needs_clamp_)
     scrollable_area->ClampScrollOffsetAfterOverflowChange();
   delete needs_clamp_;
   needs_clamp_ = nullptr;
 }
 
 }  // namespace blink