Consider using different names for some typedefs to reduce conflicts

[sigmundch]

We currently have typedefs like:

typedef Float32List = JSAny?

WHen imported together with dart:typed_data this causes issues. One can hide it from the import, but potentially we may want to make the default set of public type names to not overlap with those commonly used together from other core libraries?

[kevmoo]

Or maybe https://github.com/dart-lang/web/issues/65 ?