Move blink_perf.xml_http_request benchmark to tools/perf/contrib/ directory

tools/perf/run_benchmark

 #!/usr/bin/env python
 # Copyright 2013 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import sys
 
 from core import path_util
 from core import trybot_command
 sys.path.insert(1, path_util.GetTelemetryDir())
 
 from telemetry import benchmark_runner
 
 from chrome_telemetry_build import chromium_config
 
 
 def main():
   config = chromium_config.ChromiumConfig(
-      benchmark_dirs=[path_util.GetPerfBenchmarksDir()],
+      benchmark_dirs=[path_util.GetPerfBenchmarksDir(),
+                      path_util.GetPerfContribDir()],
       top_level_dir=path_util.GetPerfDir())
   return benchmark_runner.main(config, [trybot_command.Trybot])
 
 
 if __name__ == '__main__':
   sys.exit(main())