Use --use-cps-ir compiler option in the test script to run dart2js with the new backend.

tools/bots/compiler.py

Index: tools/bots/compiler.py
diff --git a/tools/bots/compiler.py b/tools/bots/compiler.py
index 276b19634fcf1f39e94707a700a44162b01ce5f2..a784a03ca7cf27c6848ad828d095c548c26e625e 100644
--- a/tools/bots/compiler.py
+++ b/tools/bots/compiler.py
@@ -359,10 +359,7 @@ def RunCompilerTests(build_info):
   if build_info.checked: test_flags += ['--checked']
   if build_info.minified: test_flags += ['--minified']
   if build_info.host_checked: test_flags += ['--host-checked']
-  # cps backend does not work with batch mode due to the environment variable
-  # setting.
-  if build_info.batch and not build_info.cps_ir:
-    test_flags += ['--dart2js-batch']
+  if build_info.batch: test_flags += ['--dart2js-batch']
   if build_info.builder_tag: test_flags += ['--builder-tag=' +
                                              build_info.builder_tag]
   if build_info.cps_ir: test_flags += ['--cps-ir']