Support `void` as generic argument.

pkg/compiler/lib/src/js_backend/namer.dart

Index: pkg/compiler/lib/src/js_backend/namer.dart
diff --git a/pkg/compiler/lib/src/js_backend/namer.dart b/pkg/compiler/lib/src/js_backend/namer.dart
index 01ce064a1ff3915a5e2194aa090bd3cc947a64e5..efe1e99f16ef2ee61767135a173ec308e3c7acd3 100644
--- a/pkg/compiler/lib/src/js_backend/namer.dart
+++ b/pkg/compiler/lib/src/js_backend/namer.dart
@@ -636,8 +636,6 @@ class Namer {
         return asName(typedefTag);
       case JsGetName.FUNCTION_TYPE_TAG:
         return asName(functionTypeTag);
-      case JsGetName.FUNCTION_TYPE_VOID_RETURN_TAG:
-        return asName(functionTypeVoidReturnTag);
       case JsGetName.FUNCTION_TYPE_RETURN_TYPE_TAG:
         return asName(functionTypeReturnTypeTag);
       case JsGetName.FUNCTION_TYPE_REQUIRED_PARAMETERS_TAG:
@@ -1539,8 +1537,6 @@ class Namer {
 
   String get functionTypeTag => r'func';
 
-  String get functionTypeVoidReturnTag => r'v';
-
   String get functionTypeReturnTypeTag => r'ret';
 
   String get functionTypeRequiredParametersTag => r'args';