Set attached flag before we call didAddScrollbar

third_party/WebKit/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 377 matching lines @@
   }
 }
 
 void FrameView::ScrollbarManager::setHasHorizontalScrollbar(bool hasScrollbar) {
   if (hasScrollbar == hasHorizontalScrollbar())
     return;
 
   if (hasScrollbar) {
     m_hBar = createScrollbar(HorizontalScrollbar);
     m_scrollableArea->layoutBox()->document().view()->addChild(m_hBar.get());
+    m_hBarIsAttached = 1;
     m_scrollableArea->didAddScrollbar(*m_hBar, HorizontalScrollbar);
     m_hBar->styleChanged();
-    m_hBarIsAttached = 1;
   } else {
     m_hBarIsAttached = 0;
     destroyScrollbar(HorizontalScrollbar);
   }
 
   m_scrollableArea->setScrollCornerNeedsPaintInvalidation();
 }
 
 void FrameView::ScrollbarManager::setHasVerticalScrollbar(bool hasScrollbar) {
   if (hasScrollbar == hasVerticalScrollbar())
     return;
 
   if (hasScrollbar) {
     m_vBar = createScrollbar(VerticalScrollbar);
     m_scrollableArea->layoutBox()->document().view()->addChild(m_vBar.get());
+    m_vBarIsAttached = 1;
     m_scrollableArea->didAddScrollbar(*m_vBar, VerticalScrollbar);
     m_vBar->styleChanged();
-    m_vBarIsAttached = 1;
   } else {
     m_vBarIsAttached = 0;
     destroyScrollbar(VerticalScrollbar);
   }
 
   m_scrollableArea->setScrollCornerNeedsPaintInvalidation();
 }
 
 Scrollbar* FrameView::ScrollbarManager::createScrollbar(
     ScrollbarOrientation orientation) {
@@ skipping 4670 matching lines @@
     std::unique_ptr<CompositorAnimationTimeline> timeline) {
   m_animationTimeline = std::move(timeline);
 }
 
 void FrameView::setAnimationHost(
     std::unique_ptr<CompositorAnimationHost> host) {
   m_animationHost = std::move(host);
 }
 
 }  // namespace blink