removing some unused default ctors now that nsDerivedSafe can handle it.

no bug, r+sr=bz

content/shared/public/nsStyleContext.h

@@ -150,10 +150,6 @@ public:
 #endif
 
 protected:
-  // A default ctor is needed to use nsRefPtr (nsDerivedSafe) with this class.
-  // It should never be called.
-  nsStyleContext() { NS_NOTREACHED("nsStyleContext default ctor"); }
-
   void AppendChild(nsStyleContext* aChild);
   void RemoveChild(nsStyleContext* aChild);
 

content/xbl/src/nsXBLPrototypeBinding.h

@@ -188,9 +188,6 @@ protected:
   void GetNestedChildren(nsIAtom* aTag, nsIContent* aContent,
                          nsISupportsArray** aList);
 
-  // This should never be called, but is necessary to satisfy nsRefPtr.
-  nsXBLPrototypeBinding() { NS_NOTREACHED("nsXBLPrototypeBinding default ctor"); }
-
 protected:
   // Internal helper class for managing our IID table.
   class nsIIDKey : public nsHashKey {

layout/style/nsStyleContext.h

@@ -150,10 +150,6 @@ public:
 #endif
 
 protected:
-  // A default ctor is needed to use nsRefPtr (nsDerivedSafe) with this class.
-  // It should never be called.
-  nsStyleContext() { NS_NOTREACHED("nsStyleContext default ctor"); }
-
   void AppendChild(nsStyleContext* aChild);
   void RemoveChild(nsStyleContext* aChild);