Bug 900898 part 1.  Give dom::TypedArray structs a no-argument constructor.  r=smaug
Bug 900898 part 2.  Move to using Nullable<TypedArray> to represent possibly-null TypedArray structs.  r=smaug
Bug 900898 part 3.  Support typed arrays inside dictionaries.  r=smaug
Bug 900898 part 4.  Support typed arrays inside sequences and variadics.  r=smaug
Bug 901285.  Allow trailing comma in WebIDL enums.  r=khuey