I really don't think Wolves need armour, they can defend themselves as well as players quite fine. Like Broccoli_Monkey said, the armour is used for protection because Horses can't generate health similarly to how Wolves or Ocelots can. If you have food with you, you are capable of regenerating the Wolf's health.
This thread has a short explanation, and the rest is mostly self explanatory... By looking at the image given by the original poster, you can understand the general appearance... The following is what needs to be added to the thread:
• How can Wolf Armor be obtained?
• What is its durability, if it has any?
• Why would this make a great feature?
I myself do not support this suggestion, not because of my inability to actually build upon a vague suggestion, but because the idea itself doesn't seem right... While a horse can't defend itself, a wolf can. Wolves are attackers, meaning that they can fend for themselves and others, while horses are a form of transportation. A horse needs armor in order to protect themselves, while wolves don't need as much protection... Not to mention how over powered this is; a player with a pack of wolves is already somewhat over powering in battle, so it is easy to assume that a player with armored wolves is much more dangerous. Neither a player or a group of Zombies can possibly defeat an army of diamond-clad fighters, without at least a sword with fire aspect.