Split js_backend_cps_ir tests into multiple test units.

tests/compiler/dart2js/js_backend_cps_ir_closures_test.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.
+// VMOptions=-DUSE_CPS_IR=true
 
-// Tests of interceptors.
+// Tests of closures.
 
 library closures_test;
 
-import 'js_backend_cps_ir_test.dart';
+import 'js_backend_cps_ir.dart';
 
 const List<TestEntry> tests = const [
   const TestEntry("""
 main(x) {
   a() {
     return x;
   }
   x = x + '1';
   print(a());
 }
@@ skipping 96 matching lines @@
       v1 = 1;
       box_01.i_0 = J.getInterceptor(i).$add(i, v1);
       box_0 = box_01;
     } else {
       P.print(a.call$0());
       return null;
     }
   }
 }"""),
 ];
+
+void main() {
+  runTests(tests);
+}