Implement Element.scrollIntoView for scroll-behavior: smooth.

third_party/WebKit/Source/core/page/scrolling/ScrollingCoordinator.h

Index: third_party/WebKit/Source/core/page/scrolling/ScrollingCoordinator.h
diff --git a/third_party/WebKit/Source/core/page/scrolling/ScrollingCoordinator.h b/third_party/WebKit/Source/core/page/scrolling/ScrollingCoordinator.h
index 161f9786cb93e753a2bf908d47b81f734ff7ef67..5f34430486001a3e926872eba550b5247a41efc5 100644
--- a/third_party/WebKit/Source/core/page/scrolling/ScrollingCoordinator.h
+++ b/third_party/WebKit/Source/core/page/scrolling/ScrollingCoordinator.h
@@ -49,6 +49,7 @@ class Page;
 class PaintLayer;
 class Region;
 class ScrollableArea;
+class ProgrammaticScrollCoordinator;
 class WebLayerTreeView;
 class WebScrollbarLayer;
 
@@ -134,6 +135,8 @@ class CORE_EXPORT ScrollingCoordinator final
     return m_programmaticScrollAnimatorTimeline.get();
   }
 
+  ProgrammaticScrollCoordinator* programmaticScrollCoordinator();
+
   // For testing purposes only. This ScrollingCoordinator is reused between
   // layout test, and must be reset for the results to be valid.
   void reset();
@@ -186,6 +189,8 @@ class CORE_EXPORT ScrollingCoordinator final
   bool m_wasFrameScrollable;
 
   MainThreadScrollingReasons m_lastMainThreadScrollingReasons;
+
+  Member<ProgrammaticScrollCoordinator> m_programmaticScrollCoordinator;

[bokan, 2017/02/21 21:33:01]

What should happen if two separate scrollable DIVs have an element get
scrollIntoView'd? I would expect them both to scroll simultaneously but having
this be a field on ScrollingCoordinator would mean they'd happen one after the
other, right? Perhaps this should be a member on ScrollableArea?

[sunyunjia, 2017/02/24 19:11:48]

Well, on a second thought, there might be conflict if we try to scroll the two
separate DIVs simultaneously. So I think they should happen one after the other
and the current design is good for now.

 };
 
 }  // namespace blink