Changed the animation mode enum to PRUint16 (removed the enum) in nsIPresContext so we could use the constants
from imgIContainer. (changes from dcone's review comments)
Bug 2586 r=dcone sr=attinasi
git-svn-id: svn://10.0.0.236/trunk@108058 18797224-902f-48f8-a5cc-f745e15eee43