[foozzie] Pass startup test

This makes sure the harness passes when called without test case.

BUG=chromium:673246
NOTRY=true
TBR=tandrii@chromium.org,mbarbella@chromium.org

Review-Url: https://codereview.chromium.org/2623743004
Cr-Commit-Position: refs/heads/master@{#42183}

tools/foozzie/v8_foozzie.py

@@ -101,9 +101,13 @@ def parse_args():
   parser.add_argument(
       '--second-d8',
       help='optional path to second d8 executable, default: same as first')
-  parser.add_argument('testcase', help='path to test case')
+  parser.add_argument('testcase', help='path to test case', nargs='?')
   options = parser.parse_args()
 
+  if not options.testcase:
+    # Don't check further as we want to bail out early without test case.
+    return options
+
   # Ensure we make a sane comparison.
   assert (options.first_arch != options.second_arch or
           options.first_config != options.second_config) , (
@@ -185,6 +189,10 @@ def fail_bailout(output, ignore_by_output_fun):
 def main():
   options = parse_args()
 
+  if not options.testcase:
+    print '# V8 correctness - pass - no test file given'
+    return RETURN_PASS
+
   # Suppressions are architecture and configuration specific.
   suppress = v8_suppressions.get_suppression(
       options.first_arch, options.first_config,