Rename 'instant' value of scroll-behavior CSS property to 'auto'

Source/core/frame/FrameView.cpp

 /*
  * Copyright (C) 1998, 1999 Torben Weis <weis@kde.org>
  *                     1999 Lars Knoll <knoll@kde.org>
  *                     1999 Antti Koivisto <koivisto@kde.org>
  *                     2000 Dirk Mueller <mueller@kde.org>
  * Copyright (C) 2004, 2005, 2006, 2007, 2008 Apple Inc. All rights reserved.
  *           (C) 2006 Graham Dennis (graham.dennis@gmail.com)
  *           (C) 2006 Alexey Proskuryakov (ap@nypop.com)
  * Copyright (C) 2009 Google Inc. All rights reserved.
  *
@@ skipping 1507 matching lines @@
     cancelProgrammaticScrollAnimation();
     TemporaryChange<bool> changeInProgrammaticScroll(m_inProgrammaticScroll, true);
     m_maintainScrollPositionAnchor = nullptr;
 
     DoublePoint newScrollPosition = adjustScrollPositionWithinRange(scrollPoint);
     if (newScrollPosition == scrollPositionDouble())
         return;
 
     if (scrollBehavior == ScrollBehaviorAuto) {
         RenderObject* renderer = m_frame->document()->documentElement() ? m_frame->document()->documentElement()->renderer() : 0;
-        if (renderer)
-            scrollBehavior = renderer->style()->scrollBehavior();
+        if (renderer && renderer->style()->scrollBehavior() == ScrollBehaviorSmooth)
+            scrollBehavior = ScrollBehaviorSmooth;
         else
             scrollBehavior = ScrollBehaviorInstant;
     }
 
     if (scrollBehavior == ScrollBehaviorInstant) {
         DoubleSize newOffset(newScrollPosition.x(), newScrollPosition.y());
         updateScrollbars(newOffset);
     } else {
         programmaticallyScrollSmoothlyToOffset(toFloatPoint(newScrollPosition));
     }
@@ skipping 2422 matching lines @@
         return;
 
     ScrollableArea::setScrollOrigin(origin);
 
     // Update if the scroll origin changes, since our position will be different if the content size did not change.
     if (updatePositionAtAll && updatePositionSynchronously)
         updateScrollbars(scrollOffsetDouble());
 }
 
 } // namespace blink