Fix path construction in perf runner.

tools/run_perf.py

 #!/usr/bin/env python
 # Copyright 2014 the V8 project authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 """
 Performance runner for d8.
 
 Call e.g. with tools/run-perf.py --arch ia32 some_suite.json
 
@@ skipping 516 matching lines @@
     if file_on_host in self.pushed:
       return
     else:
       self.pushed.add(file_on_host)
 
     logging.info("adb push %s %s" % (file_on_host, file_on_device))
     self.adb.Push(file_on_host, file_on_device)
 
   def PreTests(self, node, path):
     suite_dir = os.path.abspath(os.path.dirname(path))
-    bench_dir = os.path.join(suite_dir,
-                             os.path.normpath(os.path.join(*node.path)))
+    if node.path:
+      bench_dir = os.path.join(suite_dir,
+                               os.path.normpath(os.path.join(*node.path)))
+    else:
+      bench_dir = suite_dir
 
     self._PushFile(self.shell_dir, node.binary)
     if isinstance(node, Runnable):
       self._PushFile(bench_dir, node.main)
     for resource in node.resources:
       self._PushFile(bench_dir, resource)
 
   def Run(self, runnable, count):
     cache = cache_control.CacheControl(self.device)
     cache.DropRamCaches()
@@ skipping 111 matching lines @@
 
   if options.json_test_results:
     results.WriteToFile(options.json_test_results)
   else:  # pragma: no cover
     print results
 
   return min(1, len(results.errors))
 
 if __name__ == "__main__":  # pragma: no cover
   sys.exit(Main(sys.argv[1:]))