[test] Switch off perf data feature on swarming.

tools/testrunner/local/perfdata.py

 # 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
 #       copyright notice, this list of conditions and the following
 #       disclaimer in the documentation and/or other materials provided
@@ skipping 100 matching lines @@
     self.closed = True
 
   def GetStore(self, arch, mode):
     with self.lock:
       if not arch in self.stores:
         self.stores[arch] = {}
       modes = self.stores[arch]
       if not mode in modes:
         modes[mode] = PerfDataStore(self.datadir, arch, mode)
       return modes[mode]
+
+
+class NullPerfDataStore(object):
+  def UpdatePerfData(self, test):
+    pass
+
+  def FetchPerfData(self, test):
+    return None
+
+
+class NullPerfDataManager(object):
+  def __init__(self):
+    pass
+
+  def GetStore(self, *args, **kwargs):
+    return NullPerfDataStore()
+
+  def close(self):
+    pass
+
+
+def GetPerfDataManager(context, datadir):
+  if context.use_perf_data:
+    return PerfDataManager(datadir)
+  else:
+    return NullPerfDataManager()