Merges two WK fixes for RenderLayer::backgroundIsKnownToBeOpaque.

Source/core/rendering/RenderLayer.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 5532 matching lines @@
 }
 
 bool RenderLayer::backgroundIsKnownToBeOpaqueInRect(const LayoutRect& localRect) const
 {
     if (!isSelfPaintingLayer() && !hasSelfPaintingLayerDescendant())
         return false;
 
     if (paintsWithTransparency(PaintBehaviorNormal))
         return false;
 
+    // We can't use hasVisibleContent(), because that will be true if our renderer is hidden, but some child
+    // is visible and that child doesn't cover the entire rect.
+    if (renderer()->style()->visibility() != VISIBLE)
+        return false;
+
     if (paintsWithFilters() && renderer()->style()->filter().hasFilterThatAffectsOpacity())
         return false;
 
     // FIXME: Handle simple transforms.
     if (paintsWithTransform(PaintBehaviorNormal))
         return false;
 
     // FIXME: Remove this check.
     // This function should not be called when layer-lists are dirty.
     // It is somehow getting triggered during style update.
     if (m_zOrderListsDirty || m_normalFlowListDirty)
         return false;
 
     // FIXME: We currently only check the immediate renderer,
     // which will miss many cases.
-    return renderer()->backgroundIsKnownToBeOpaqueInRect(localRect)
-        || listBackgroundIsKnownToBeOpaqueInRect(posZOrderList(), localRect)
+    if (renderer()->backgroundIsKnownToBeOpaqueInRect(localRect))
+        return true;
+
+    // We can't consult child layers if we clip, since they might cover
+    // parts of the rect that are clipped out.
+    if (renderer()->hasOverflowClip())
+        return false;
+
+    return listBackgroundIsKnownToBeOpaqueInRect(posZOrderList(), localRect)
         || listBackgroundIsKnownToBeOpaqueInRect(negZOrderList(), localRect)
         || listBackgroundIsKnownToBeOpaqueInRect(normalFlowList(), localRect);
 }
 
 bool RenderLayer::listBackgroundIsKnownToBeOpaqueInRect(const Vector<RenderLayer*>* list, const LayoutRect& localRect) const
 {
     if (!list || list->isEmpty())
         return false;
 
     for (Vector<RenderLayer*>::const_reverse_iterator iter = list->rbegin(); iter != list->rend(); ++iter) {
@@ skipping 872 matching lines @@
     }
 }
 
 void showLayerTree(const WebCore::RenderObject* renderer)
 {
     if (!renderer)
         return;
     showLayerTree(renderer->enclosingLayer());
 }
 #endif