Add --modules=node support

lib/src/codegen/js_names.dart

Index: lib/src/codegen/js_names.dart
diff --git a/lib/src/codegen/js_names.dart b/lib/src/codegen/js_names.dart
index c84991f6be1f40d124e284be69edac8ded985dc3..a07b1f727a1b8ae2060996feddda83e804c85b39 100644
--- a/lib/src/codegen/js_names.dart
+++ b/lib/src/codegen/js_names.dart
@@ -281,6 +281,12 @@ bool invalidVariableName(String keyword, {bool strictMode: true}) {
     case "static":
     case "yield":
       return strictMode;
+
+    // Node refuses these:

[Jennifer Messerly, 2016/01/29 00:32:31]

Any more info on these? What's the error message say, and under what conditions
do they not work?

it's a little scary, usually JS is careful to not take away names that worked,
it breaks backwards compat. Hence a lot of names are only blacklisted in "strict
mode"

(we try and be careful to only blacklist names when we absolutely need to.)

[ochafik, 2016/01/29 09:38:17]

Dropped these, not needed now...

+    case "async":

[Jennifer Messerly, 2016/01/29 00:32:31]

this could be related to https://tc39.github.io/ecmascript-asyncawait/, but I'd
be surprised if it isn't backwards compatible.

[ochafik, 2016/01/29 09:38:17]

My bad, now fixed (I had a weird collision of async lib import alias and async
function declaration, sometime before the exportName -> name fix)

+    case "dynamic":
+    case "void":

[Jennifer Messerly, 2016/01/29 00:32:31]

it looks like "void" is already covered, above? So this is a duplicate case

[ochafik, 2016/01/29 09:38:17]

Done.

+      return true;
   }
   return false;
 }