Implement Element.scrollIntoView for scroll-behavior: smooth.

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

 /*
  * Copyright (C) 2006 Apple Computer, 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 189 matching lines @@
   ScrollbarOverlayColorThemeDark,
   ScrollbarOverlayColorThemeLight
 };
 
 enum ScrollBehavior {
   ScrollBehaviorAuto,
   ScrollBehaviorInstant,
   ScrollBehaviorSmooth,
 };
 
+enum ScrollBlock {
+  ScrollBlockStart,
+  ScrollBlockEnd,
+};
+
 // The result of an attempt to scroll. If didScroll is true, then
 // unusedScrollDelta gives the amount of the scroll delta that was not consumed
 // by scrolling.
 struct ScrollResult {
   STACK_ALLOCATED();
   explicit ScrollResult()
       : didScrollX(false),
         didScrollY(false),
         unusedScrollDeltaX(0),
         unusedScrollDeltaY(0) {}
@@ skipping 43 matching lines @@
       NOTREACHED();
       return ScrollGranularity::ScrollByPrecisePixel;
   }
 }
 
 typedef unsigned ScrollbarControlPartMask;
 
 }  // namespace blink
 
 #endif