Make sure we set "should flatten transform" correctly.

Source/core/rendering/compositing/CompositedLayerMapping.cpp

 /*
  * Copyright (C) 2009, 2010, 2011 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 1078 matching lines @@
 
     if (m_backgroundLayer)
         m_backgroundLayer->setDrawsContent(hasPaintedContent);
 }
 
 void CompositedLayerMapping::updateChildrenTransform()
 {
     if (GraphicsLayer* childTransformLayer = layerForChildrenTransform()) {
         childTransformLayer->setTransform(owningLayer().perspectiveTransform());
         childTransformLayer->setTransformOrigin(FloatPoint3D(childTransformLayer->size().width() * 0.5f, childTransformLayer->size().height() * 0.5f, 0.f));
-        bool hasPerspective = false;
-        if (RenderStyle* style = m_owningLayer.renderer()->style())
-            hasPerspective = style->hasPerspective();
-        if (hasPerspective)
-            childTransformLayer->setShouldFlattenTransform(false);
+    }
 
-        // Note, if the target is the scrolling layer, we need to ensure that the
-        // scrolling content layer doesn't flatten the transform. (It would be nice
-        // if we could apply transform to the scrolling content layer, but that's
-        // too late, we need the children transform to be applied _before_ the
-        // scrolling offset.)
-        if (childTransformLayer == m_scrollingLayer.get())
-            m_scrollingContentsLayer->setShouldFlattenTransform(false);
-    }
+    updateShouldFlattenTransform();
 }
 
 // Return true if the layers changed.
 bool CompositedLayerMapping::updateClippingLayers(bool needsAncestorClip, bool needsDescendantClip)
 {
     bool layersChanged = false;
 
     if (needsAncestorClip) {
         if (!m_ancestorClippingLayer) {
             m_ancestorClippingLayer = createGraphicsLayer(CompositingReasonLayerForAncestorClip);
@@ skipping 24 matching lines @@
 }
 
 bool CompositedLayerMapping::updateChildTransformLayer(bool needsChildTransformLayer)
 {
     bool layersChanged = false;
 
     if (needsChildTransformLayer) {
         if (!m_childTransformLayer) {
             m_childTransformLayer = createGraphicsLayer(CompositingReasonLayerForPerspective);
             m_childTransformLayer->setDrawsContent(false);
-            m_childTransformLayer->setShouldFlattenTransform(false);
             layersChanged = true;
         }
     } else if (m_childTransformLayer) {
         m_childTransformLayer->removeFromParent();
         m_childTransformLayer = nullptr;
         layersChanged = true;
     }
 
     return layersChanged;
 }
@@ skipping 105 matching lines @@
     if ((mode & ApplyToCoreLayers) && mapping->childTransformLayer())
         f(mapping->childTransformLayer());
     if ((mode & ApplyToCoreLayers) && mapping->ancestorClippingLayer())
         f(mapping->ancestorClippingLayer());
     if (((mode & ApplyToCoreLayers) || (mode & ApplyToContentLayers)) && mapping->mainGraphicsLayer())
         f(mapping->mainGraphicsLayer());
     if ((mode & ApplyToCoreLayers) && mapping->clippingLayer())
         f(mapping->clippingLayer());
     if ((mode & ApplyToCoreLayers) && mapping->scrollingLayer())
         f(mapping->scrollingLayer());
+    if ((mode & ApplyToCoreLayers) && mapping->scrollingBlockSelectionLayer())
+        f(mapping->scrollingBlockSelectionLayer());
     if (((mode & ApplyToCoreLayers) || (mode & ApplyToContentLayers)) && mapping->scrollingContentsLayer())
         f(mapping->scrollingContentsLayer());
     if (((mode & ApplyToCoreLayers) || (mode & ApplyToContentLayers)) && mapping->foregroundLayer())
         f(mapping->foregroundLayer());
 
     if ((mode & ApplyToSquashingLayer) && mapping->squashingLayer())
         f(mapping->squashingLayer());
 
     if (((mode & ApplyToMaskLayers) || (mode & ApplyToContentLayers)) && mapping->maskLayer())
         f(mapping->maskLayer());
@@ skipping 45 matching lines @@
     bool shouldFlatten;
 };
 
 void CompositedLayerMapping::updateShouldFlattenTransform()
 {
     // All CLM-managed layers that could affect a descendant layer should update their
     // should-flatten-transform value (the other layers' transforms don't matter here).
     UpdateShouldFlattenTransformFunctor functor = { !m_owningLayer.shouldPreserve3D() };
     ApplyToGraphicsLayersMode mode = ApplyToCoreLayers;
     ApplyToGraphicsLayers(this, functor, mode);
+
+    // Note, if we apply perspective, we have to set should flatten differently
+    // so that the transform propagates to child layers correctly.
+    if (GraphicsLayer* childTransformLayer = layerForChildrenTransform()) {
+        bool hasPerspective = false;
+        if (RenderStyle* style = m_owningLayer.renderer()->style())
+            hasPerspective = style->hasPerspective();
+        if (hasPerspective)
+            childTransformLayer->setShouldFlattenTransform(false);
+
+        // Note, if the target is the scrolling layer, we need to ensure that the
+        // scrolling content layer doesn't flatten the transform. (It would be nice
+        // if we could apply transform to the scrolling content layer, but that's
+        // too late, we need the children transform to be applied _before_ the
+        // scrolling offset.)
+        if (childTransformLayer == m_scrollingLayer.get()) {
+            m_scrollingContentsLayer->setShouldFlattenTransform(false);
+            m_scrollingBlockSelectionLayer->setShouldFlattenTransform(false);
+        }
+    }
 }
 
 bool CompositedLayerMapping::updateForegroundLayer(bool needsForegroundLayer)
 {
     bool layerChanged = false;
     if (needsForegroundLayer) {
         if (!m_foregroundLayer) {
             m_foregroundLayer = createGraphicsLayer(CompositingReasonLayerForForeground);
             m_foregroundLayer->setDrawsContent(true);
             m_foregroundLayer->setPaintingPhase(GraphicsLayerPaintForeground);
@@ skipping 883 matching lines @@
     } else if (graphicsLayer == m_scrollingBlockSelectionLayer.get()) {
         name = "Scrolling Block Selection Layer";
     } else {
         ASSERT_NOT_REACHED();
     }
 
     return name;
 }
 
 } // namespace WebCore