Reland "Recompute overflow after transform changes"

Source/core/rendering/RenderLayerScrollableArea.cpp

 /*
  * Copyright (C) 2006, 2007, 2008, 2009, 2010, 2011, 2012 Apple Inc. All rights reserved.
  *
  * Portions are Copyright (C) 1998 Netscape Communications Corporation.
  *
  * Other contributors:
  *   Robert O'Callahan <roc+@cs.cmu.edu>
  *   David Baron <dbaron@fas.harvard.edu>
  *   Christian Biesinger <cbiesinger@web.de>
  *   Randall Jesup <rjesup@wgate.com>
@@ skipping 753 matching lines @@
     RenderLayer* layer = this->layer();
     if (layer->hasCompositedLayerMapping() && layer->compositedLayerMapping()->updateGraphicsLayerConfiguration(GraphicsLayerUpdater::ForceUpdate))
         layer->compositor()->setCompositingLayersNeedRebuild();
 }
 
 void RenderLayerScrollableArea::updateAfterCompositingChange()
 {
     layer()->updateScrollingStateAfterCompositingChange();
 }
 
+void RenderLayerScrollableArea::updateAfterOverflowRecalc()
+{
+    computeScrollDimensions();
+    if (Scrollbar* horizontalScrollbar = this->horizontalScrollbar()) {
+        int clientWidth = m_box.pixelSnappedClientWidth();
+        horizontalScrollbar->setProportion(clientWidth, overflowRect().width());
+    }
+    if (Scrollbar* verticalScrollbar = this->verticalScrollbar()) {
+        int clientHeight = m_box.pixelSnappedClientHeight();
+        verticalScrollbar->setProportion(clientHeight, overflowRect().height());
+    }
+
+    bool hasHorizontalOverflow = this->hasHorizontalOverflow();
+    bool hasVerticalOverflow = this->hasVerticalOverflow();
+    bool autoHorizontalScrollBarChanged = m_box.hasAutoHorizontalScrollbar() && (hasHorizontalScrollbar() != hasHorizontalOverflow);
+    bool autoVerticalScrollBarChanged = m_box.hasAutoVerticalScrollbar() && (hasVerticalScrollbar() != hasVerticalOverflow);
+    if (autoHorizontalScrollBarChanged || autoVerticalScrollBarChanged)
+        m_box.setNeedsLayout();
+}
+
 IntSize RenderLayerScrollableArea::clampScrollOffset(const IntSize& scrollOffset) const
 {
     int maxX = scrollWidth() - m_box.pixelSnappedClientWidth();
     int maxY = scrollHeight() - m_box.pixelSnappedClientHeight();
 
     int x = std::max(std::min(scrollOffset.width(), maxX), 0);
     int y = std::max(std::min(scrollOffset.height(), maxY), 0);
     return IntSize(x, y);
 }
 
@@ skipping 738 matching lines @@
 void RenderLayerScrollableArea::setForceNeedsCompositedScrolling(ForceNeedsCompositedScrollingMode mode)
 {
     if (m_forceNeedsCompositedScrolling == mode)
         return;
 
     m_forceNeedsCompositedScrolling = mode;
     layer()->didUpdateNeedsCompositedScrolling();
 }
 
 } // Namespace WebCore