Fixed Inconsistent behaviour of custom-scrollbar

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 902 matching lines @@
         // We need to ensure that we mark up all renderers up to the RenderView
         // for paint invalidation. This simplifies our code as we just always
         // do a full tree walk.
         if (RenderObject* container = rootForThisLayout->container())
             container->setMayNeedPaintInvalidation(true);
     } // Reset m_layoutSchedulingEnabled to its previous value.
 
     if (!inSubtreeLayout && !toRenderView(rootForThisLayout)->document().printing())
         adjustViewSize();
 
+    if (rootForThisLayout->needsLayout())
+        performLayout(rootForThisLayout, inSubtreeLayout);

[esprehn, 2014/09/19 05:06:52]

Other places call adjustViewSize without a second layout, are you sure this is
right? Should adjustViewSize do this?

[MuVen, 2014/09/19 16:19:30]

During adjustViewSize call, in the API FrameView::setContentsSize, after calling
ScrollView::setContentsSize(size); sets the rootObject needsLayout.

+
     layer->updateLayerPositionsAfterLayout();
 
     if (m_doFullPaintInvalidation)
         renderView()->compositor()->fullyInvalidatePaint();
     renderView()->compositor()->didLayout();
 
     m_layoutCount++;
 
     if (AXObjectCache* cache = rootForThisLayout->document().axObjectCache()) {
         const KURL& url = rootForThisLayout->document().url();
@@ skipping 2043 matching lines @@
 void FrameView::willRemoveScrollbar(Scrollbar* scrollbar, ScrollbarOrientation orientation)
 {
     ScrollableArea::willRemoveScrollbar(scrollbar, orientation);
     if (AXObjectCache* cache = axObjectCache()) {
         cache->remove(scrollbar);
         cache->handleScrollbarUpdate(this);
     }
 }
 
 } // namespace blink