See Can I legally update, republish and sell an old electronic game?
The point of that question - the fact that the game is not on the market anymore - is not relevant to you, but the basics of trademarks are still relevant.
You can't legally copy the game - the images, artwork, sounds and/or the overall design - and turn it into your game. That's called infringement, and the maker of the browser game could pursue you in civil court.
You could copy parts of the game into a new game, but in that case, Fair Use comes into play, and you need to carefully consider that concept and your usage: In the US, when is fair use a defense to copyright infringement?
Why not contact the author of the browser game and ask if you can adapt an Android version?
