Cleanup machine based on the state in configuration file for mini installer test.

chrome/test/mini_installer/visitor.py

+# Copyright 2017 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.
+
+class Visitor(object):
+  """Traverse one property of a state's dict"""
+  CONDITION = 'condition'
+
+  def __init__(self, variable_expander):
+    self._variable_expander = variable_expander
+
+  def Traverse(self, property_value):
+    for entry_name, entry_value in property_value.iteritems():
+      if Visitor.CONDITION in entry_value and not self._EvaluateCondition(
+          self._variable_expander.Expand(entry_value[Visitor.CONDITION])):
+        continue
+      self._VisitEntry(entry_name, entry_value)
+
+  def _EvaluateCondition(self, condition):
+    """Evaluates |condition| using eval().
+
+    Args:
+      condition: A condition string.
+
+    Returns:
+      The result of the evaluated condition.
+    """
+    return eval(condition, {'__builtins__': {'False': False, 'True': True}})
+
+  def _VisitEntry(self, entry_name, entry_value):
+    raise NotImplementedError()