Add test on dart2js static analysis of method type parameters.

tests/language/generic_functions_test.dart

Index: tests/language/generic_functions_test.dart
diff --git a/tests/language/generic_functions_test.dart b/tests/language/generic_functions_test.dart
index 814163a33f9051e4d488b7bf3c554e3a35fd83f2..e3f6cafa3d7f00fadf21390a5fc3cae42703bc8f 100644
--- a/tests/language/generic_functions_test.dart
+++ b/tests/language/generic_functions_test.dart
@@ -55,19 +55,16 @@ class BinaryTreeNode<K extends Comparable<K>, V> {
   }
 }
 
-// Use fresh type variables.
 BinaryTreeNode<K2, V2> insertOpt<K2 extends Comparable<K2>, V2>(
     BinaryTreeNode<K2, V2> t, K2 key, V2 value) {
   return (t == null) ? new BinaryTreeNode(key, value) : t.insert(key, value);
 }
 
-// Reuse type variables [K], [V] to test shadowing.
 BinaryTreeNode<K, U> mapOpt<K extends Comparable<K>, V, U>(
     BinaryTreeNode<K, V> t, U f(V x)) {
   return (t == null) ? null : t.map<U>(f);
 }
 
-// Use fresh [K2], shadowing [V].
 S foldPreOpt<K2 extends Comparable<K2>, V, S>(
     BinaryTreeNode<K2, V> t, S init, S f(V t, S s)) {
   return (t == null) ? init : t.foldPre<S>(init, f);