[Telemetry] Fix 'important' field of certain Values being non-boolean

tools/telemetry/telemetry/value/__init__.py

 # 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.
 """
 The Value hierarchy provides a way of representing the values measurements
 produce such that they can be merged across runs, grouped by page, and output
 to different targets.
 
 The core Value concept provides the basic functionality:
 - association with a page, may be none
@@ skipping 39 matching lines @@
           represents results for multiple pages.
       name: A value name string, may contain a dot. Values from the same test
           with the same prefix before the dot may be considered to belong to
           the same chart.
       units: A units string.
       important: Whether the value is "important". Causes the value to appear
           by default in downstream UIs.
       description: A string explaining in human-understandable terms what this
           value represents.
     """
+    if page is not None:
+      # TODO(eakuefner): Change this to isinstance once page is refactored.
+      assert type(page).__name__ == 'Page'

[nednguyen, 2015/02/13 19:09:21]

Actually, let's left page alone for now because the abstraction we have been
cheating here is 'user_story' :-(

[eakuefner, 2015/02/13 19:29:13]

Fair enough. I did some fiddling in the bug tracker and also put a ref to the
bug in question here.

+    assert isinstance(name, str)
+    assert isinstance(units, str)
+    assert isinstance(important, bool)
+    if description is not None:
+      assert isinstance(description, str)

[nednguyen, 2015/02/13 19:09:21]

assert (not description) or isinstance(description, str)

[eakuefner, 2015/02/13 19:29:13]

Done, except I think (not description) is not quite correct because that will be
True if description is False so I've gone for (description is None).

+
     self.page = page
     self.name = name
     self.units = units
     self.important = important
     self.description = description
 
   def IsMergableWith(self, that):
     return (self.units == that.units and
             type(self) == type(that) and
             self.important == that.important)
@@ skipping 229 matching lines @@
   whereas telemetry represents values with a chart_name.trace_name convention,
   where chart_name is optional. This convention is also used by chart_json.
 
   This converts from the telemetry convention to the buildbot convention,
   returning a 2-tuple (measurement_name, trace_name).
   """
   if '.' in value_name:
     return value_name.split('.', 1)
   else:
     return value_name, value_name