Adjusts dart2js backend to handle method type arguments.

tests/language/generic_methods_type_expression_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.
+//
+// DartOptions=--generic-method-syntax
+
+/// Dart test on the usage of method type arguments in type expressions. With
+/// '--generic-method-syntax', the type argument is available at runtime,
+/// but erased to `dynamic`.
+
+library generic_methods_type_expression_test;
+
+import "package:expect/expect.dart";
+
+bool f1<T>(Object o) => o is T;
+
+bool f2<T>(Object o) => o is List<T>;
+
+bool f3<T>(Object o) => o is! T;
+
+bool f4<T>(Object o) => o is! List<T>;
+
+T f5<T>(Object o) => o as T;
+
+List<T> f6<T>(Object o) => o as List<T>;
+
+Type f7<T>() => T;
+
+class TypeValue<X> {
+  Type get value => X;
+}
+
+Type f8<T>() => new TypeValue<List<T>>().value;
+
+main() {
+  String s = "Hello!";
+  List<String> ss = <String>[s];
+  Expect.throws(() => f1<int>(42), (e) => e is TypeError);
+  Expect.throws(() => f1<String>(42), (e) => e is TypeError);
+  Expect.equals(f2<int>(<int>[42]), true);
+  Expect.equals(f2<String>(<int>[42]), true); // `is List<dynamic>` is true.
+  Expect.throws(() => f3<int>(42), (e) => e is TypeError);
+  Expect.throws(() => f3<String>(42), (e) => e is TypeError);
+  Expect.equals(f4<int>(<int>[42]), false);
+  Expect.equals(f4<String>(<int>[42]), false); // `is! List<dynamic>` is false.
+  Expect.throws(() => f5<String>(s), (e) => e is TypeError);
+  Expect.throws(() => f5<int>(s), (e) => e is TypeError);
+  Expect.equals(f6<String>(ss), ss);
+  Expect.equals(f6<int>(ss), ss); // `as List<dynamic>` succeeds.
+  Expect.throws(() => f7<int>(), (e) => e is TypeError);
+  Expect.equals(f8<int>(), List); // Returns `List<dynamic>`.
+}