Give more meaningful name to m_which in CustomElementLifecycleCallbacks

Source/core/dom/custom/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 32 matching lines @@
     virtual ~CustomElementLifecycleCallbacks() { }
 
     enum CallbackType {
         None                     = 0,
         CreatedCallback          = 1 << 0,
         AttachedCallback         = 1 << 1,
         DetachedCallback         = 1 << 2,
         AttributeChangedCallback = 1 << 3
     };
 
-    bool hasCallback(CallbackType type) const { return m_which & type; }
+    bool hasCallback(CallbackType type) const { return m_callbackType & type; }
 
     virtual void created(Element*) = 0;
     virtual void attached(Element*) = 0;
     virtual void detached(Element*) = 0;
     virtual void attributeChanged(Element*, const AtomicString& name, const AtomicString& oldValue, const AtomicString& newValue) = 0;
 
 protected:
-    CustomElementLifecycleCallbacks(CallbackType which) : m_which(which) { }
+    CustomElementLifecycleCallbacks(CallbackType type) : m_callbackType(type) { }
 
 private:
-    CallbackType m_which;
+    CallbackType m_callbackType;
 };
 
 }
 
 #endif // CustomElementLifecycleCallbacks_h