Add required_initial_confidence to legacy bisect.

tools/run-bisect-perf-regression.py

Index: tools/run-bisect-perf-regression.py
diff --git a/tools/run-bisect-perf-regression.py b/tools/run-bisect-perf-regression.py
index 7641617c5426bde916ba3730643b729733279f95..8dce2aeaf664c9559e26f7ca2b989e6efeaadf76 100755
--- a/tools/run-bisect-perf-regression.py
+++ b/tools/run-bisect-perf-regression.py
@@ -209,6 +209,10 @@ def _CreateBisectOptionsFromConfig(config):
   if config.has_key('improvement_direction'):
     opts_dict['improvement_direction'] = int(config['improvement_direction'])
 
+  if config.has_key('required_initial_confidence'):
+    opts_dict['required_initial_confidence'] = int(
+        config['required_initial_confidence'])
+
   if config.has_key('target_arch'):
     opts_dict['target_arch'] = config['target_arch']