[test] Print how test runner is called on swarming.

tools/run-tests.py

 #!/usr/bin/env python
 #
 # Copyright 2012 the V8 project authors. All rights reserved.
 # Redistribution and use in source and binary forms, with or without
 # modification, are permitted provided that the following conditions are
 # met:
 #
 #     * Redistributions of source code must retain the above copyright
 #       notice, this list of conditions and the following disclaimer.
 #     * Redistributions in binary form must reproduce the above
@@ skipping 579 matching lines @@
   # Use the v8 root as cwd as some test cases use "load" with relative paths.
   os.chdir(BASE_DIR)
 
   parser = BuildOptions()
   (options, args) = parser.parse_args()
   if not ProcessOptions(options):
     parser.print_help()
     return 1
   SetupEnvironment(options)
 
+  if options.swarming:
+    # Swarming doesn't print how isolated commands are called. Lets make this
+    # less cryptic by printing it ourselves.
+    print ' '.join(sys.argv)
+
   exit_code = 0
   if not options.no_presubmit:
     print ">>> running presubmit tests"
     exit_code = subprocess.call(
         [sys.executable, join(BASE_DIR, "tools", "presubmit.py")])
 
   suite_paths = utils.GetSuitePaths(join(BASE_DIR, "test"))
 
   # Use default tests if no test configuration was provided at the cmd line.
   if len(args) == 0:
@@ skipping 227 matching lines @@
         "--coverage-dir=%s" % options.sancov_dir])
     except:
       print >> sys.stderr, "Error: Merging sancov files failed."
       exit_code = 1
 
   return exit_code
 
 
 if __name__ == "__main__":
   sys.exit(Main())