Merged FrameView and LayoutBox scrolling in EventHandler.

third_party/WebKit/Source/core/layout/LayoutView.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009 Apple Inc. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
  * This library is distributed in the hope that it will be useful,
@@ skipping 1004 matching lines @@
     // LayoutView of the main frame is responsible for painting base background.
     if (!document().ownerElement())
         setHasBoxDecorationBackground(true);
 }
 
 bool LayoutView::allowsOverflowClip() const
 {
     return document().settings() && document().settings()->rootLayerScrolls();
 }
 
+ScrollResult LayoutView::scroll(ScrollGranularity granularity, const FloatSize& delta)
+{

[szager1, 2016/03/02 19:14:35]

I think you should probably add this at the top of this method (skobes@ should
confirm):

if (document().settings() && document().settings()->rootLayerScrolls())
    return LayoutBlockFlow::scroll(granularity, delta);

[bokan, 2016/03/02 20:37:13]

Thanks for the heads up. This shouldn't change the flow from what we do today -
we're just calling applyScrollDelta from here rather than EventHandler, but I
can believe it's wrong today. I'll let skobes@ comment.

[skobes, 2016/03/02 23:26:30]

LocalFrame::applyScrollDelta calls through FrameView::scrollableArea() so it
will do the right thing in root layer scrolling mode.

That said, perhaps this overload can go away with scroll customization, given
that we already have logic in Element::nativeApplyScroll to call
LocalFrame::applyScrollDelta?

[bokan, 2016/03/02 23:33:19]

I think you're right. Right now, I'm just trying to remove some of the crazy
duplication we've got going on in EventHandler. Though I like the symmetry of
calling code not having to make a distinction between LayoutBoxes.

+    if (!frameView())
+        return ScrollResult();
+
+    return frame()->applyScrollDelta(granularity, delta, false);
+}
+
 } // namespace blink