Implement Element.scrollIntoView for scroll-behavior: smooth.

third_party/WebKit/Source/platform/scroll/ScrollableArea.h

 /*
  * Copyright (C) 2008, 2011 Apple Inc. All Rights Reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 32 matching lines @@
 namespace blink {
 
 class CompositorAnimationHost;
 class CompositorAnimationTimeline;
 class GraphicsLayer;
 class HostWindow;
 class LayoutBox;
 class LayoutObject;
 class PaintLayer;
 class ProgrammaticScrollAnimator;
+class ProgrammaticScrollCoordinator;
 struct ScrollAlignment;
 class ScrollAnchor;
 class ScrollAnimatorBase;
 class CompositorAnimationTimeline;
 
 enum IncludeScrollbarsInRect {
   ExcludeScrollbars,
   IncludeScrollbars,
 };
 
@@ skipping 10 matching lines @@
   // per http://dev.w3.org/csswg/cssom-view/#normalize-non_finite-values.
   static float normalizeNonFiniteScroll(float value) {
     return std::isfinite(value) ? value : 0.0;
   }
 
   // The window that hosts the ScrollableArea. The ScrollableArea will
   // communicate scrolls and repaints to the host window in the window's
   // coordinate space.
   virtual HostWindow* getHostWindow() const { return 0; }
 
+  virtual ProgrammaticScrollCoordinator* getProgrammaticScrollCoordinator()

[bokan, 2017/03/28 16:29:53]

I don't think this should be part of this class' interface. As mentioned above,
Page is probably a better place and I think everything has access to Page.

[sunyunjia, 2017/03/31 15:42:45]

When each scrollableArea finishes its scroll, ProgrammaticScrollAnimator(PSA)
will notify SmoothScrollSequencer so that the next scrollableArea can start
scroll (see PSA in this patch). Unfortunately, neither of PSA and ScrollableArea
has access to Page. In fact, implementations of
ScrollableArea(PaintLayerScrollableArea, FrameView, RootFrameViewport) have
different path to access page. So I guess the best way to access
SmoothScrollSequencer from PSA is through ScrollableArea's interface? 

[bokan, 2017/03/31 20:30:46]

Ah, yes...ScrollableArea is in platform. It's a bit verbose but
ScrollableArea->layoutBox()->document().page() should do the trick. You'll have
to nullcheck layoutBox but if it doesn't have a layoutbox it wont be scrollable
so you can just abort. I'd add a private helper where you need it to get the
Page this way.

+      const {
+    return 0;
+  }
+
   virtual ScrollResult userScroll(ScrollGranularity, const ScrollOffset&);
 
   virtual void setScrollOffset(const ScrollOffset&,
                                ScrollType,
                                ScrollBehavior = ScrollBehaviorInstant);
   virtual void scrollBy(const ScrollOffset&,
                         ScrollType,
                         ScrollBehavior = ScrollBehaviorInstant);
   void setScrollOffsetSingleAxis(ScrollbarOrientation,
                                  float,
                                  ScrollType,
                                  ScrollBehavior = ScrollBehaviorInstant);
 
   // Scrolls the area so that the given rect, given in the document's content
   // coordinates, such that it's visible in the area. Returns the new location
   // of the input rect relative once again to the document.
   // Note, in the case of a Document container, such as FrameView, the output
   // will always be the input rect since scrolling it can't change the location
   // of content relative to the document, unlike an overflowing element.
   virtual LayoutRect scrollIntoView(const LayoutRect& rectInContent,
                                     const ScrollAlignment& alignX,
                                     const ScrollAlignment& alignY,
-                                    ScrollType = ProgrammaticScroll);
+                                    ScrollType = ProgrammaticScroll,
+                                    bool isSmooth = false);
 
   static bool scrollBehaviorFromString(const String&, ScrollBehavior&);
 
   void contentAreaWillPaint() const;
   void mouseEnteredContentArea() const;
   void mouseExitedContentArea() const;
   void mouseMovedInContentArea() const;
   void mouseEnteredScrollbar(Scrollbar&);
   void mouseExitedScrollbar(Scrollbar&);
   void mouseCapturedScrollbar();
@@ skipping 333 matching lines @@
   // vertical-lr / ltr            NO                      NO
   // vertical-lr / rtl            NO                      YES
   // vertical-rl / ltr            YES                     NO
   // vertical-rl / rtl            YES                     YES
   IntPoint m_scrollOrigin;
 };
 
 }  // namespace blink
 
 #endif  // ScrollableArea_h