Reverse style resolution to avoid N^2 walk when building the render tree

Source/core/css/SiblingTraversalStrategies.h

Index: Source/core/css/SiblingTraversalStrategies.h
diff --git a/Source/core/css/SiblingTraversalStrategies.h b/Source/core/css/SiblingTraversalStrategies.h
index 8751e94a2cad4010993af6d0fc0a4d1d9b7a728f..65885c93549f52c416dcee7237b34c627ae21a06 100644
--- a/Source/core/css/SiblingTraversalStrategies.h
+++ b/Source/core/css/SiblingTraversalStrategies.h
@@ -78,14 +78,8 @@ inline bool DOMSiblingTraversalStrategy::isLastOfType(Element* element, const Qu
 inline int DOMSiblingTraversalStrategy::countElementsBefore(Element* element) const
 {
     int count = 0;
-    for (const Element* sibling = element->previousElementSibling(); sibling; sibling = sibling->previousElementSibling()) {
-        unsigned index = sibling->childIndex();
-        if (index) {
-            count += index;
-            break;
-        }
+    for (const Element* sibling = element->previousElementSibling(); sibling; sibling = sibling->previousElementSibling())
         count++;
-    }
 
     return count;
 }
@@ -104,8 +98,14 @@ inline int DOMSiblingTraversalStrategy::countElementsOfTypeBefore(Element* eleme
 inline int DOMSiblingTraversalStrategy::countElementsAfter(Element* element) const
 {
     int count = 0;
-    for (const Element* sibling = element->nextElementSibling(); sibling; sibling = sibling->nextElementSibling())
+    for (const Element* sibling = element->nextElementSibling(); sibling; sibling = sibling->nextElementSibling()) {
+        unsigned index = sibling->childIndex();
+        if (index) {
+            count += index;
+            break;
+        }
         ++count;
+    }
 
     return count;
 }