Remove PostAttachCallbacks and replace with something more specialized

Source/core/svg/SVGElement.cpp

Index: Source/core/svg/SVGElement.cpp
diff --git a/Source/core/svg/SVGElement.cpp b/Source/core/svg/SVGElement.cpp
index 84f7baceb80009ca48e6c1b59d13e4c6b2c0d54c..d0648dccdef1c8a04f4d95ee009536bf63d10b3a 100644
--- a/Source/core/svg/SVGElement.cpp
+++ b/Source/core/svg/SVGElement.cpp
@@ -115,11 +115,7 @@ SVGElement::~SVGElement()
 
 void SVGElement::willRecalcStyle(StyleRecalcChange change)
 {
-    // FIXME: This assumes that when shouldNotifyRendererWithIdenticalStyles() is true
-    // the change came from a SMIL animation, but what if there were non-SMIL changes
-    // since then? I think we should remove the shouldNotifyRendererWithIdenticalStyles
-    // check.
-    if (!hasSVGRareData() || shouldNotifyRendererWithIdenticalStyles())
+    if (!hasSVGRareData())
         return;
     // If the style changes because of a regular property change (not induced by SMIL animations themselves)
     // reset the "computed style without SMIL style properties", so the base value change gets reflected.