Introduce UserStory & UserStorySet classes.

tools/telemetry/telemetry/user_story/user_story_set.py

Index: tools/telemetry/telemetry/user_story/user_story_set.py
diff --git a/tools/telemetry/telemetry/user_story/user_story_set.py b/tools/telemetry/telemetry/user_story/user_story_set.py
new file mode 100644
index 0000000000000000000000000000000000000000..cee65d422427a987f81f919537a9e18996913749
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+++ b/tools/telemetry/telemetry/user_story/user_story_set.py
@@ -0,0 +1,47 @@
+# Copyright 2014 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.
+
+from telemetry import user_story as user_story_module
+
+
+class UserStorySet(object):
+  def __init__(self):
+    self.user_stories = []
+
+  def AddUserStory(self, user_story):
+    assert isinstance(user_story, user_story_module.UserStory)
+    self.user_stories.append(user_story)
+
+  @classmethod
+  def Name(cls):
+    """ Returns the string name of this UserStorySet.
+    Note that this should be a classmethod so test_runner script can match
+    user story class with its name specified in the run command:
+    'Run <User story test name> <User story class name>'
+    """
+    return cls.__module__.split('.')[-1]
+
+  @classmethod
+  def Description(cls):
+    """ Return a string explaining in human-understandable terms what this
+    user story represents.
+    Note that this should be a classmethod so test_runner script can
+    display user stories' names along their descriptions in the list commmand.
+    """
+    if cls.__doc__:
+      return cls.__doc__.splitlines()[0]
+    else:
+      return ''
+
+  def __iter__(self):
+    return self.user_stories.__iter__()
+
+  def __len__(self):
+    return len(self.user_stories)
+
+  def __getitem__(self, key):
+    return self.user_stories[key]
+
+  def __setitem__(self, key, value):
+    self.user_stories[key] = value