Add a WebDocument::watchCssSelectors(selectors)

Source/core/dom/Element.h

Index: Source/core/dom/Element.h
diff --git a/Source/core/dom/Element.h b/Source/core/dom/Element.h
index f36faaa74de0af39c0a30c3da488b5d0fb004bc1..09b2797d2370b3cac87fbcae4a61677d38fde6cf 100644
--- a/Source/core/dom/Element.h
+++ b/Source/core/dom/Element.h
@@ -751,6 +751,12 @@ private:
 
     virtual RenderStyle* virtualComputedStyle(PseudoId pseudoElementSpecifier = NOPSEUDO) { return computedStyle(pseudoElementSpecifier); }
 
+    enum AddOrRemove {
+        Add,
+        Remove,
+    };
+    void updateCallbackSelectors(AddOrRemove);
+
     // cloneNode is private so that non-virtual cloneElementWithChildren and cloneElementWithoutChildren
     // are used instead.
     virtual PassRefPtr<Node> cloneNode(bool deep) OVERRIDE;