Provide a refactoring option to add a variable as a member

It would be super nice to have a refactoring option that adds a variable to the class it's used within. For example, pressing alt + enter over mPicture below could bring up an option entitled "Add Member Variable":

ImageWidget(const QPicture &picture) : mPicture(picture) {
}

This would be useful when writing quick test cases for bugs, for example.