Removed main-thread one dimensional scrolling paths.

third_party/WebKit/Source/core/dom/Element.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2001 Peter Kelly (pmk@post.com)
  *           (C) 2001 Dirk Mueller (mueller@kde.org)
  *           (C) 2007 David Smith (catfish.man@gmail.com)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2012, 2013 Apple Inc. All rights reserved.
  *           (C) 2007 Eric Seidel (eric@webkit.org)
  *
  * This library is free software; you can redistribute it and/or
@@ skipping 551 matching lines @@
         if (document().frame()->applyScrollDelta(ScrollByPrecisePixel, delta, scrollState.isBeginning()).didScroll()) {
             scrolled = true;
             scrollState.consumeDeltaNative(scrollState.deltaX(), scrollState.deltaY());
         }
     } else {
         if (!layoutObject())
             return;
         LayoutBoxItem curBox = LayoutBoxItem(toLayoutBox(layoutObject())).enclosingBox();
         // FIXME: Native scrollers should only consume the scroll they
         // apply. See crbug.com/457765.
-        if (deltaX && curBox.scroll(ScrollLeft, ScrollByPrecisePixel, deltaX).didScroll) {
+        // TODO(bokan): I think the scroll deltas here are backwards.

[skobes, 2016/02/29 18:52:47]

Can you clarify this TODO?  Why are they backwards and where should they be
corrected?

[bokan, 2016/03/01 05:56:24]

Done. (I have a follow up patch which fixes the TODO I'll put up shortly).

+        if (deltaX && curBox.scroll(ScrollByPrecisePixel, FloatSize(-deltaX, 0)).didScrollX) {
             scrollState.consumeDeltaNative(scrollState.deltaX(), 0);
             scrolled = true;
         }
 
-        if (deltaY && curBox.scroll(ScrollUp, ScrollByPrecisePixel, deltaY).didScroll) {
+        if (deltaY && curBox.scroll(ScrollByPrecisePixel, FloatSize(0, -deltaY)).didScrollY) {
             scrollState.consumeDeltaNative(0, scrollState.deltaY());
             scrolled = true;
         }
     }
 
     if (!scrolled)
         return;
 
     // We need to setCurrentNativeScrollingElement in both the
     // distributeScroll and applyScroll default implementations so
@@ skipping 3052 matching lines @@
 {
 #if ENABLE(OILPAN)
     if (hasRareData())
         visitor->trace(elementRareData());
     visitor->trace(m_elementData);
 #endif
     ContainerNode::trace(visitor);
 }
 
 } // namespace blink