Implement Custom Elements' entered and left document callbacks.

Source/core/dom/CustomElementLifecycleCallbacks.h

 /*
  * Copyright (C) 2013 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 27 matching lines @@
 
 class Element;
 
 class CustomElementLifecycleCallbacks : public RefCounted<CustomElementLifecycleCallbacks> {
 public:
     virtual ~CustomElementLifecycleCallbacks() { }
 
     bool hasCreated() const { return m_which & Created; }
     virtual void created(Element*) = 0;
 
+    bool hasEnteredDocument() const { return m_which & EnteredDocument; }
+    virtual void enteredDocument(Element*) = 0;

[Yuta Kitamura, 2013/07/08 03:40:49]

As far as I know, Blink's (WebKit's) standard of callback/delegate names is:
- "didDoSomething()" (to be called after DoSomething) or
- "willDoSomething()" (to be called before DoSomething)

However, if this name is exposed to the user, your naming may be fine.

As a side note, "hasEnteredDocument()" is somewhat confusing as it look like
present perfect tense. But I don't think of good alternatives. Maybe
"hasEnteredDocumentCallback()".

+
+    bool hasLeftDocument() const { return m_which & LeftDocument; }
+    virtual void leftDocument(Element*) = 0;
+
     bool hasAttributeChanged() const { return m_which & AttributeChanged; }
     virtual void attributeChanged(Element*, const AtomicString& name, const AtomicString& oldValue, const AtomicString& newValue) = 0;
 
     enum CallbackType {
         None             = 0,
         Created          = 1 << 0,
-        AttributeChanged = 1 << 1
+        EnteredDocument  = 1 << 1,
+        LeftDocument     = 1 << 2,
+        AttributeChanged = 1 << 3
     };
 
 protected:
     CustomElementLifecycleCallbacks(CallbackType which) : m_which(which) { }
 
 private:
     CallbackType m_which;
 };
 
 }
 
 #endif // CustomElementLifecycleCallbacks_h