Revert of Recompute overflow after transform changes

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 63346d4f89457c81cfbbebc152ad939841139841..ade78168df78b1ffb94ea9961c8028ae6a4593cc 100644
--- a/Source/core/rendering/RenderObject.cpp
+++ b/Source/core/rendering/RenderObject.cpp
@@ -1854,17 +1854,24 @@ StyleDifference RenderObject::adjustStyleDifference(StyleDifference diff, unsign
 {
     // FIXME: The calls to hasDirectReasonsForCompositing are using state that may not be up to date.
     DisableCompositingQueryAsserts disabler;
-
-    if (contextSensitiveProperties & ContextSensitivePropertyTransform && isSVG())
-        diff = StyleDifferenceLayout;
-
-    // If transform changed, and the layer does not paint into its own separate backing, then we need to repaint.
-    if (contextSensitiveProperties & ContextSensitivePropertyTransform  && diff <= StyleDifferenceRepaintLayer) {
+    // If transform changed, and the layer does not paint into its own separate backing, then we need to do a layout.
+    // FIXME: The comment above is what the code does, but it is technically not following spec. This means we will
+    // not to layout for 3d transforms, but we should be invoking a simplified relayout. Is it possible we are avoiding
+    // doing this for some performance reason at this time?
+    if (contextSensitiveProperties & ContextSensitivePropertyTransform) {
         // Text nodes share style with their parents but transforms don't apply to them,
         // hence the !isText() check.
-        if (!isText() && (!hasLayer() || !toRenderLayerModelObject(this)->layer()->hasDirectReasonsForCompositing()))
-            diff = StyleDifferenceRepaintLayer;
-        else if (diff < StyleDifferenceRecompositeLayer)
+        // FIXME: when transforms are taken into account for overflow, we will need to do a layout.
+        if (!isText() && (!hasLayer() || !toRenderLayerModelObject(this)->layer()->hasDirectReasonsForCompositing())) {
+            // We need to set at least SimplifiedLayout, but if PositionedMovementOnly is already set
+            // then we actually need SimplifiedLayoutAndPositionedMovement.
+            if (!hasLayer())
+                diff = StyleDifferenceLayout; // FIXME: Do this for now since SimplifiedLayout cannot handle updating floating objects lists.
+            else if (diff < StyleDifferenceLayoutPositionedMovementOnly)
+                diff = StyleDifferenceSimplifiedLayout;
+            else if (diff < StyleDifferenceSimplifiedLayout)
+                diff = StyleDifferenceSimplifiedLayoutAndPositionedMovement;
+        } else if (diff < StyleDifferenceRecompositeLayer)
             diff = StyleDifferenceRecompositeLayer;
     }
 
@@ -1941,18 +1948,6 @@ inline bool RenderObject::hasImmediateNonWhitespaceTextChildOrPropertiesDependen
     return false;
 }
 
-void RenderObject::markContainingBlocksForOverflowRecalc()
-{
-    for (RenderBlock* container = containingBlock(); container && !container->childNeedsOverflowRecalcAfterStyleChange(); container = container->containingBlock())
-        container->setChildNeedsOverflowRecalcAfterStyleChange(true);
-}
-
-void RenderObject::setNeedsOverflowRecalcAfterStyleChange()
-{
-    setSelfNeedsOverflowRecalcAfterStyleChange(true);
-    markContainingBlocksForOverflowRecalc();
-}
-
 void RenderObject::setStyle(PassRefPtr<RenderStyle> style)
 {
     ASSERT(style);
@@ -2004,13 +1999,11 @@ void RenderObject::setStyle(PassRefPtr<RenderStyle> style)
             setNeedsLayoutAndPrefWidthsRecalc();
         else if (updatedDiff == StyleDifferenceLayoutPositionedMovementOnly)
             setNeedsPositionedMovementLayout();
-    }
-
-    if (contextSensitiveProperties & ContextSensitivePropertyTransform && !needsLayout()) {
-        if (RenderBlock* container = containingBlock())
-            container->setNeedsOverflowRecalcAfterStyleChange();
-        if (isBox())
-            toRenderBox(this)->updateLayerTransform();
+        else if (updatedDiff == StyleDifferenceSimplifiedLayoutAndPositionedMovement) {
+            setNeedsPositionedMovementLayout();
+            setNeedsSimplifiedNormalFlowLayout();
+        } else if (updatedDiff == StyleDifferenceSimplifiedLayout)
+            setNeedsSimplifiedNormalFlowLayout();
     }
 
     if (updatedDiff == StyleDifferenceRepaint || updatedDiff == StyleDifferenceRepaintLayer) {
@@ -2143,7 +2136,7 @@ void RenderObject::styleDidChange(StyleDifference diff, const RenderStyle* oldSt
     if (!m_parent)
         return;
 
-    if (diff == StyleDifferenceLayout) {
+    if (diff == StyleDifferenceLayout || diff == StyleDifferenceSimplifiedLayout) {
         RenderCounter::rendererStyleChanged(*this, oldStyle, m_style.get());
 
         // If the object already needs layout, then setNeedsLayout won't do
@@ -2154,12 +2147,13 @@ void RenderObject::styleDidChange(StyleDifference diff, const RenderStyle* oldSt
         if (needsLayout() && oldStyle->position() != m_style->position())
             markContainingBlocksForLayout();
 
-        // Ditto.
-        if (needsOverflowRecalcAfterStyleChange() && oldStyle->position() != m_style->position())
-            markContainingBlocksForOverflowRecalc();
-
         if (diff == StyleDifferenceLayout)
             setNeedsLayoutAndPrefWidthsRecalc();
+        else
+            setNeedsSimplifiedNormalFlowLayout();
+    } else if (diff == StyleDifferenceSimplifiedLayoutAndPositionedMovement) {
+        setNeedsPositionedMovementLayout();
+        setNeedsSimplifiedNormalFlowLayout();
     } else if (diff == StyleDifferenceLayoutPositionedMovementOnly)
         setNeedsPositionedMovementLayout();