SupportsKey* key = (SupportsKey*)aKey; return PRBool(mSupports == key->mSupports);
URLKey* key = (URLKey*)aKey; return mURL->Equals(key->mURL);
  virtual PRBool Equals(const nsHashKey* aKey) const  {    SupportsKey* key = (SupportsKey*)aKey;    return PRBool(mSupports == key->mSupports);  }