In 1984, what do Winston's dreams about his mother, the golden country, and the dark-haired girl reveal about him?
I see Winston's dreams about his mother and his betrayal of her a bit differently. His grabbing the chocolate for himself suggests that there are certain drives that are almost out of his/our control. Stealing food from your mother/sister is a horrible act, but it suggests a kind of malleability that foreshadows what is going to happen at the end of the story. Winston's betrayal of Julia is horrible; "Do it to Julia" may be the saddest words in modern literature, but they are, in the world of 1984, unavoidable. In the long run, the state "breaks" everyone.
I think that Winston's dreams of the golden country and the dark-haired girl represent his "romantic" side, his belief that things can be better; it is akin to his belief that if there is going to be "salvation," it will come from the Proles. These dreams show how little Winston is aware of the present reality and are tied to his belief (which is contrary to his expressed knowledge) that he can keep the diary without any consequences. Perhaps it is these ideas that make his final undoing so painful.
Winston's dreams about his mother show the reader that he has a rather callous side and foreshadows his betrayal of Julia; even though he regrets the way he treated his mother and his sister. However what he dreams about reveals that he is inherently selfish and that the need for self preservation and survival overcomes such strong bonds as filial loyalty.
The golden country links to his mother in that it highlights his obsession with history. He feels that the past might have been idyllic and compared to the present, it is. By dreaming about the golden country, Winston is highlighting the fact that he wants a pastoral lifestyle, full of freedom and the ability to be an individual.
His dreams about the dark-haired girl reveal his dark side. What he dreams about is quite horrific and yet at the same time, almost erotic. It shows that he cannot completely suppress the animalistic side of him and that the repression the Party imposes can only go so deep. For Winston, it verges on superficial.
His dream about his mother foreshadows his betrayal of Julia on the fact that he simply feels sorry and that is it. The Golden Country symbolizes his dreams, hope, desires for freedom of thoughts and his beliefs. The dark hair girl adds a primal side to him to show he still has some deep-seated erotic desire in him in a society where making love is forbidden.