Add test on dart2js static analysis of method type parameters.

tests/language/generic_functions_test.dart

 // Copyright (c) 2016, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 /// Dart test verifying that the parser can handle type parameterization of
 /// function declarations and function invocations. Variant of code from
 /// DEP #22, adjusted to use generic top level functions.
 
 library generic_functions_test;
 
@@ skipping 37 matching lines @@
     var _fold = (BinaryTreeNode<K, V> t, S s, S f(V t, S s)) =>
         foldPreOpt<K, V, S>(t, s, f);
     S s = init;
     s = f(_value, s);
     s = _fold(_left, s, f);
     s = _fold(_right, s, f);
     return s;
   }
 }
 
-// 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);
 }
 
 class BinaryTree<K extends Comparable<K>, V> {
   final BinaryTreeNode<K, V> _root;
 
   BinaryTree._internal(this._root);
   BinaryTree.empty() : this._internal(null);
@@ skipping 18 matching lines @@
 
   sT = sT.insert(0, "");
   sT = sT.insert(1, " ");
   sT = sT.insert(2, "  ");
   sT = sT.insert(3, "   ");
 
   BinaryTree<num, num> iT = sT.map<num>((String s) => s.length);
 
   Expect.equals(iT.foldPre<num>(0, (int i, num s) => i + s), 6);
 }