Add infrastructure for partial layouts

Source/core/dom/Document.h

Index: Source/core/dom/Document.h
diff --git a/Source/core/dom/Document.h b/Source/core/dom/Document.h
index 587a094fb917721edbf9c54785573fb6fe91340f..6257630eb714ebb9ede3cf326a6c26a24ee99ceb 100644
--- a/Source/core/dom/Document.h
+++ b/Source/core/dom/Document.h
@@ -491,6 +491,7 @@ public:
     void updateStyleForNodeIfNeeded(Node*);
     void updateLayout();
     void updateLayoutIgnorePendingStylesheets();
+    void partialUpdateLayoutIgnorePendingStylesheets(Node*);
     PassRefPtr<RenderStyle> styleForElementIgnoringPendingStylesheets(Element*);
     PassRefPtr<RenderStyle> styleForPage(int pageIndex);
 
@@ -1123,6 +1124,8 @@ private:
 
     void seamlessParentUpdatedStylesheets();
 
+    void recalcStyleForLayoutIgnoringPendingStylesheets();
+
     PassRefPtr<NodeList> handleZeroPadding(const HitTestRequest&, HitTestResult&) const;
 
     void loadEventDelayTimerFired(Timer<Document>*);