[test] Switch off perf data feature on swarming.

tools/testrunner/local/perfdata.py

Index: tools/testrunner/local/perfdata.py
diff --git a/tools/testrunner/local/perfdata.py b/tools/testrunner/local/perfdata.py
index 2979dc48661b9b48662a37a0555133b470ee25c3..29ebff773a5dd6a4ca2d31104d5c46910d19aa87 100644
--- a/tools/testrunner/local/perfdata.py
+++ b/tools/testrunner/local/perfdata.py
@@ -118,3 +118,29 @@ class PerfDataManager(object):
       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()