Implement Custom Elements inserted and removed callbacks.

Source/core/dom/CustomElementCallback.h

Index: Source/core/dom/CustomElementCallback.h
diff --git a/Source/core/dom/CustomElementCallback.h b/Source/core/dom/CustomElementCallback.h
index d71e35afeeddd2d552ecf339fcb1ab626dbcc76a..c701651061c98c72e979172f1fd98d5d62ad0803 100644
--- a/Source/core/dom/CustomElementCallback.h
+++ b/Source/core/dom/CustomElementCallback.h
@@ -41,15 +41,23 @@ class CustomElementCallback : public RefCounted<CustomElementCallback> {
 public:
     virtual ~CustomElementCallback() { }
 
-    bool hasReady() const { return m_which == Ready; }
+    bool hasReady() const { return m_which & Ready; }
     virtual void ready(Element*) = 0;
 
-protected:
+    bool hasInserted() const { return m_which & Inserted; }
+    virtual void inserted(Element*) = 0;
+
+    bool hasRemoved() const { return m_which & Removed; }
+    virtual void removed(Element*) = 0;
+
     enum CallbackType {
-        None,
-        Ready
+        None     = 0,
+        Ready    = 1 << 0,
+        Inserted = 1 << 1,
+        Removed  = 1 << 2
     };
 
+protected:
     CustomElementCallback(CallbackType which) : m_which(which) { }
 
 private: