First version of typr propagation in the new IR.

tests/compiler/dart2js/js_backend_cps_ir_control_flow.dart

 // Copyright (c) 2014, 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.
 
 // Tests of control flow statements.
 
 library control_flow_tests;
 
 import 'js_backend_cps_ir_test.dart';
 
@@ skipping 98 matching lines @@
     P.print(2);
   }
   P.print(3);
   return null;
 }"""),
 const TestEntry("""
 main() {
   if (1) {
     print('bad');
   } else {
-    print('ok');
+    print('good');
   }
 }""","""
 function() {
-  P.print("bad");
+  P.print("good");
+  return null;
+}"""),
+  const TestEntry("""
+foo() => 2;
+main() {
+  if (foo()) {
+    print('bad');
+  } else {
+    print('good');
+  }
+}""","""
+function() {
+  V.foo();
+  P.print("good");
   return null;
 }"""),
 ];