Typed arrays not shimmed when using ECMASCRIPT3

Since Uint8Array and its friends are not part of the ECMASCRIPT3 spec, I assumed that they would be shimmed for compatibility when using `--language_out=ECMASCRIPT3`. E.g., something like this:

var a = new Uint8Array([1, 2]);

=>

var a = window.Uint8Array ? new Uint8Array([1, 2]) : [1, 2];

And likewise, although IE 10+ supports some Uint8Array methods, it doesn't support all of them, like slice:

a.slice ? a.slice() : Array.prototype.slice.call(a);

Using ECMASCRIPT3 as the language_out, no transformation is performed. E.g. running this:

java -jar compiler.jar --compilation_level ADVANCED_OPTIMIZATIONS --new_type_inf --warning_level VERBOSE --language_in ECMASCRIPT_NEXT --language_out ECMASCRIPT3 \
--output_wrapper ";(function() {%output%}());" --js test.js --js_output_file=test.min.js --module_resolution NODE

on this:

var a = new Uint8Array([1, 2]);
console.log(a[0]);
console.log(a.slice(1));

produces this:

;(function() {var a=new Uint8Array([1,2]);console.log(a[0]);console.log(a.slice(1));}());

Since typed arrays are part of the language definition, shouldn't ECMASCRIPT3 shim them? Also, is there any other configuration I should be changing?

Link to appspot test: https://closure-compiler.appspot.com/home#code%3D%252F%252F%2520%253D%253DClosureCompiler%253D%253D%250A%252F%252F%2520%2540compilation_level%2520ADVANCED_OPTIMIZATIONS%250A%252F%252F%2520%2540output_file_name%2520default.js%250A%252F%252F%2520%2540language_out%2520ECMASCRIPT3%250A%252F%252F%2520%253D%253D%252FClosureCompiler%253D%253D%250A%250A%252F%252F%2520ADD%2520YOUR%2520CODE%2520HERE%250A%250Avar%2520u%2520%253D%2520new%2520Uint8Array(%255B1%252C%25202%255D)%253B%250Avar%2520v%2520%253D%2520u.slice()%253B%250Aalert(v%255B0%255D)%253B

(Also, as always, thanks for all your work on Closure Compiler - it's made JS development much better for me.)