RAL: Eliminate n^2 walk to find repaint containers

Source/core/rendering/RenderObject.cpp

Index: Source/core/rendering/RenderObject.cpp
diff --git a/Source/core/rendering/RenderObject.cpp b/Source/core/rendering/RenderObject.cpp
index f96b3e8e279e98f33374b337fd121df94b189e8f..989b2747246aae4095a86a6379edf45fa5571644 100644
--- a/Source/core/rendering/RenderObject.cpp
+++ b/Source/core/rendering/RenderObject.cpp
@@ -1335,22 +1335,34 @@ void RenderObject::paint(PaintInfo&, const LayoutPoint&)
 {
 }
 
+bool RenderObject::isRepaintContainer() const
+{
+    return hasLayer() && toRenderLayerModelObject(this)->layer()->isRepaintContainer();
+}
+
 RenderLayerModelObject* RenderObject::containerForRepaint() const
 {
     if (!isRooted())
         return 0;
 
-    RenderLayerModelObject* repaintContainer = 0;
+    return adjustCompositedContainerForSpecialAncestors(enclosingCompositedContainer());
+}
 
-    RenderView* renderView = view();
-    if (renderView->usesCompositing()) {
+RenderLayerModelObject* RenderObject::enclosingCompositedContainer() const
+{
+    RenderLayerModelObject* container = 0;
+    if (view()->usesCompositing()) {
         // FIXME: CompositingState is not necessarily up to date for many callers of this function.
         DisableCompositingQueryAsserts disabler;
 
         if (RenderLayer* compositingLayer = enclosingLayer()->enclosingCompositingLayerForRepaint())
-            repaintContainer = compositingLayer->renderer();
+            container = compositingLayer->renderer();
     }
+    return container;
+}
 
+RenderLayerModelObject* RenderObject::adjustCompositedContainerForSpecialAncestors(RenderLayerModelObject* repaintContainer) const
+{
     if (document().view()->hasSoftwareFilters()) {
         if (RenderLayer* enclosingFilterLayer = enclosingLayer()->enclosingFilterLayer())
             return enclosingFilterLayer->renderer();
@@ -1365,7 +1377,7 @@ RenderLayerModelObject* RenderObject::containerForRepaint() const
         if (!repaintContainer || repaintContainer->flowThreadContainingBlock() != parentRenderFlowThread)
             repaintContainer = parentRenderFlowThread;
     }
-    return repaintContainer ? repaintContainer : renderView;
+    return repaintContainer ? repaintContainer : view();
 }
 
 template<typename T> PassRefPtr<JSONValue> jsonObjectForRect(const T& rect)
@@ -1511,7 +1523,7 @@ const char* RenderObject::invalidationReasonToString(InvalidationReason reason)
     return "";
 }
 
-void RenderObject::repaintTreeAfterLayout()
+void RenderObject::repaintTreeAfterLayout(RenderLayerModelObject& repaintContainer)
 {
     // If we didn't need invalidation then our children don't need as well.
     // Skip walking down the tree as everything should be fine below us.
@@ -1522,7 +1534,7 @@ void RenderObject::repaintTreeAfterLayout()
 
     for (RenderObject* child = firstChild(); child; child = child->nextSibling()) {
         if (!child->isOutOfFlowPositioned())
-            child->repaintTreeAfterLayout();
+            child->repaintTreeAfterLayout(repaintContainer);
     }
 }