Reduce invalidation on children-needs-layout 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 1de82be21a94517a11222fe0a1bc68bee7563242..c3b70da2488aee6087194550716341a5062a3f36 100644
--- a/Source/core/rendering/RenderObject.cpp
+++ b/Source/core/rendering/RenderObject.cpp
@@ -616,6 +616,19 @@ RenderFlowThread* RenderObject::locateFlowThreadContainingBlock() const
     return 0;
 }
 
+bool RenderObject::skipInvalidationWhenLaidOutChildren() const
+{
+    if (!neededLayoutBecauseOfChildren())
+        return false;
+
+    // SVG renderers need to be invalidated when their children are laid out.
+    // RenderBlocks with line boxes are responsible to invalidate them so we can't ignore them.
+    if (isSVG() || (isRenderBlock() && toRenderBlock(this)->firstLineBox()))
+        return false;
+
+    return rendererHasNoBoxEffect();
+}
+
 RenderBlock* RenderObject::firstLineBlock() const
 {
     return 0;
@@ -3504,6 +3517,7 @@ void RenderObject::clearPaintInvalidationState()
     setShouldDoFullPaintInvalidationAfterLayout(false);
     setShouldDoFullPaintInvalidationIfSelfPaintingLayer(false);
     setOnlyNeededPositionedMovementLayout(false);
+    setNeededLayoutBecauseOfChildren(false);
     setShouldInvalidateOverflowForPaint(false);
     setLayoutDidGetCalled(false);
     setMayNeedPaintInvalidation(false);