NOT FOR REVIEW - Update comp-scrolling state at a well defined point in the pipeline.

Source/core/rendering/RenderLayerCompositor.cpp

 /*
  * Copyright (C) 2009, 2010 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 200 matching lines @@
     , m_hasAcceleratedCompositing(true)
     , m_compositingTriggers(static_cast<ChromeClient::CompositingTriggerFlags>(ChromeClient::AllTriggers))
     , m_compositedLayerCount(0)
     , m_showDebugBorders(false)
     , m_showRepaintCounter(false)
     , m_reevaluateCompositingAfterLayout(false)
     , m_compositing(false)
     , m_compositingLayersNeedRebuild(false)
     , m_forceCompositingMode(false)
     , m_inPostLayoutUpdate(false)
+    // PATCH 2
+    , m_needsUpdateCompositingRequirementsState(false)
     , m_isTrackingRepaints(false)
     , m_rootLayerAttachment(RootLayerUnattached)
 #if !LOG_DISABLED
     , m_rootLayerUpdateCount(0)
     , m_obligateCompositedLayerCount(0)
     , m_secondaryCompositedLayerCount(0)
     , m_obligatoryBackingStoreBytes(0)
     , m_secondaryBackingStoreBytes(0)
 #endif
 {
@@ skipping 92 matching lines @@
         if (Page* page = this->page())
             page->chrome()->client()->scheduleCompositingLayerFlush();
     }
 }
 
 bool RenderLayerCompositor::hasAnyAdditionalCompositedLayers(const RenderLayer* rootLayer) const
 {
     return m_compositedLayerCount > (rootLayer->isComposited() ? 1 : 0);
 }
 
+// PATCH 2
+void RenderLayerCompositor::updateCompositingRequirementsState(CompositingUpdateType updateType, RenderLayer* updateRoot)
+{
+    if (!m_needsUpdateCompositingRequirementsState)
+        return;
+
+    const bool firstIteration = !updateRoot;
+    if (!updateRoot) {
+        bool needsUpdateHasOutOfFlowPositionedDescendant = false;
+        switch (updateType) {
+        case CompositingUpdateAfterStyleChange:
+            needsUpdateHasOutOfFlowPositionedDescendant = true;
+            break;
+        case CompositingUpdateAfterLayout:
+            break;
+        case CompositingUpdateOnScroll:
+        case CompositingUpdateOnCompositedScroll:
+            ASSERT_NOT_REACHED();
+            break;
+        }
+
+        updateRoot = rootRenderLayer();
+        updateRoot->updateDescendantDependentFlags();
+        if (needsUpdateHasOutOfFlowPositionedDescendant) {
+            updateRoot->updateHasOutOfFlowPositionedDescendant();
+        }
+    }
+
+    updateRoot->updateNeedsCompositedScrolling();
+
+    // In this function we update state that determines whether layers are
+    // stacking containers. We may therefore not use this concept here. Instead,
+    // we'll iterate through the tree topologically.
+    for (RenderLayer* child = updateRoot->firstChild(); child; child = child->nextSibling())
+        updateCompositingRequirementsState(updateType, child);
+
+    if (firstIteration)
+        m_needsUpdateCompositingRequirementsState = false;
+}
+
 void RenderLayerCompositor::updateCompositingLayers(CompositingUpdateType updateType, RenderLayer* updateRoot)
 {
     // Avoid updating the layers with old values. Compositing layers will be updated after the layout is finished.
     if (m_renderView->needsLayout())
         return;
 
     if (m_forceCompositingMode && !m_compositing)
         enableCompositingMode(true);
 
     if (!m_reevaluateCompositingAfterLayout && !m_compositing)
@@ skipping 2415 matching lines @@
     info.addMember(m_layerForScrollCorner, "layerForScrollCorner");
 #if ENABLE(RUBBER_BANDING)
     info.addMember(m_layerForOverhangAreas, "layerForOverhangAreas");
     info.addMember(m_contentShadowLayer, "contentShadowLayer");
     info.addMember(m_layerForTopOverhangArea, "layerForTopOverhangArea");
     info.addMember(m_layerForBottomOverhangArea, "layerForBottomOverhangArea");
 #endif
 }
 
 } // namespace WebCore