Add a WebDocument::watchCssSelectors(selectors)

Source/core/loader/FrameLoaderClient.h

Index: Source/core/loader/FrameLoaderClient.h
diff --git a/Source/core/loader/FrameLoaderClient.h b/Source/core/loader/FrameLoaderClient.h
index b9b04b851a77af65e3b6b8982fca3e0ecc60a436..df0b8eedc91d6bb768fb33eb0e68d5b2257c78f1 100644
--- a/Source/core/loader/FrameLoaderClient.h
+++ b/Source/core/loader/FrameLoaderClient.h
@@ -35,8 +35,9 @@
 #include "core/loader/NavigationPolicy.h"
 #include "core/page/LayoutMilestones.h"
 #include "core/platform/network/ResourceLoadPriority.h"
-#include <wtf/Forward.h>
-#include <wtf/Vector.h>
+#include "wtf/Forward.h"
+#include "wtf/HashSet.h"
+#include "wtf/Vector.h"
 
 typedef class _jobject* jobject;
 
@@ -158,6 +159,12 @@ namespace WebCore {
         virtual void didRunInsecureContent(SecurityOrigin*, const KURL&) = 0;
         virtual void didDetectXSS(const KURL&, bool didBlockEntirePage) = 0;
 
+#if ENABLE(CSS_CALLBACKS)
+        // Transmits the change in the set of CSS selectors with the
+        // -webkit-callback property that match any element on the frame.
+        virtual void selectorMatchChanged(const Vector<String>& addedSelectors, const Vector<String>& removedSelectors) = 0;
+#endif
+
         virtual ResourceError cancelledError(const ResourceRequest&) = 0;
         virtual ResourceError cannotShowURLError(const ResourceRequest&) = 0;
         virtual ResourceError interruptedForPolicyChangeError(const ResourceRequest&) = 0;