Reduce compositing update in Silk's toggle_drawer by 20%

Source/core/rendering/compositing/CompositedLayerMapping.cpp

Index: Source/core/rendering/compositing/CompositedLayerMapping.cpp
diff --git a/Source/core/rendering/compositing/CompositedLayerMapping.cpp b/Source/core/rendering/compositing/CompositedLayerMapping.cpp
index 3ce4290754caaf99725c2b7979cdb3f2ffe5c226..6b8d15ed6f449b8e6d8723e68525b0ff52386ec5 100644
--- a/Source/core/rendering/compositing/CompositedLayerMapping.cpp
+++ b/Source/core/rendering/compositing/CompositedLayerMapping.cpp
@@ -421,7 +421,7 @@ void CompositedLayerMapping::updateAfterLayout(UpdateAfterLayoutFlags flags)
         layerCompositor->updateCompositingDescendantGeometry(m_owningLayer->stackingNode(), m_owningLayer, flags & CompositingChildrenOnly);
 
         if (flags & IsUpdateRoot) {
-            updateGraphicsLayerGeometry();
+            updateGraphicsLayerGeometry(GraphicsLayerUpdater::ForceUpdate);

[ojan, 2014/03/05 18:29:51]

Should this have a FIXME to get rid of the ForceUpdate? Or are you figuring this
will go away entirely once we fix chicken-egg?

[abarth-chromium, 2014/03/05 23:12:19]

The idea is that this will go away once we fix the chicken/egg.  This is the egg
after layout.

             layerCompositor->updateRootLayerPosition();
             RenderLayerStackingNode* stackingContainer = m_owningLayer->stackingNode()->enclosingStackingContainerNode();
             if (!layerCompositor->compositingLayersNeedRebuild() && stackingContainer && (stackingContainer != m_owningLayer->stackingNode()))
@@ -617,11 +617,17 @@ void CompositedLayerMapping::updateSquashingLayerGeometry(const IntPoint& delta)
     }
 }
 
-void CompositedLayerMapping::updateGraphicsLayerGeometry()
+GraphicsLayerUpdater::UpdateType CompositedLayerMapping::updateGraphicsLayerGeometry(GraphicsLayerUpdater::UpdateType updateType)
 {
     // If we haven't built z-order lists yet, wait until later.
     if (m_owningLayer->stackingNode()->isStackingContainer() && m_owningLayer->stackingNode()->zOrderListsDirty())
-        return;
+        return updateType;
+
+    if (!m_needToUpdateGeometry && updateType != GraphicsLayerUpdater::ForceUpdate)
+        return updateType;
+    m_needToUpdateGeometry = false;
+    if (m_needToUpdateGeometryOfAllDecendants)
+        updateType = GraphicsLayerUpdater::ForceUpdate;
 
     // Set transform property, if it is not animating. We have to do this here because the transform
     // is affected by the layer dimensions.
@@ -783,7 +789,7 @@ void CompositedLayerMapping::updateGraphicsLayerGeometry()
 
     if (m_owningLayer->reflectionInfo() && m_owningLayer->reflectionInfo()->reflectionLayer()->hasCompositedLayerMapping()) {
         CompositedLayerMappingPtr reflectionCompositedLayerMapping = m_owningLayer->reflectionInfo()->reflectionLayer()->compositedLayerMapping();
-        reflectionCompositedLayerMapping->updateGraphicsLayerGeometry();
+        reflectionCompositedLayerMapping->updateGraphicsLayerGeometry(GraphicsLayerUpdater::ForceUpdate);
 
         // The reflection layer has the bounds of m_owningLayer->reflectionLayer(),
         // but the reflected layer is the bounds of this layer, so we need to position it appropriately.
@@ -862,6 +868,8 @@ void CompositedLayerMapping::updateGraphicsLayerGeometry()
     registerScrollingLayers();
 
     updateCompositingReasons();
+
+    return updateType;
 }
 
 void CompositedLayerMapping::registerScrollingLayers()
@@ -1849,6 +1857,23 @@ void CompositedLayerMapping::setBlendMode(blink::WebBlendMode blendMode)
     }
 }
 
+void CompositedLayerMapping::setNeedsGeometryUpdate()
+{
+    m_needToUpdateGeometryOfAllDecendants = true;
+
+    for (RenderLayer* current = m_owningLayer; current; current = current->ancestorCompositingLayer()) {

[ojan, 2014/03/05 18:57:00]

This is n^2 if it doesn't early return if m_needToUpdateGeometry is already set.
I'm fine fixing it in a followup, but please add a FIXME.

[abarth-chromium, 2014/03/05 23:12:19]

Ok, I'll add a FIXME.

+        ASSERT(current->hasCompositedLayerMapping());
+        CompositedLayerMappingPtr mapping = current->compositedLayerMapping();
+        mapping->m_needToUpdateGeometry = true;
+    }
+}
+
+void CompositedLayerMapping::willUpdateGeometryOfAllDecendants()
+{
+    ASSERT(!m_needToUpdateGeometry);
+    m_needToUpdateGeometryOfAllDecendants = false;
+}
+
 struct SetContentsNeedsDisplayFunctor {
     void operator() (GraphicsLayer* layer) const
     {