[Telemetry] Add capability for values to reference external files.

tools/telemetry/telemetry/value/string.py

Index: tools/telemetry/telemetry/value/string.py
diff --git a/tools/telemetry/telemetry/value/string.py b/tools/telemetry/telemetry/value/string.py
index b1cb6ff45eda72cd47b7d460e9b4d089e5c31b24..849db6ae25c25374ed7613871c148752387a47d6 100644
--- a/tools/telemetry/telemetry/value/string.py
+++ b/tools/telemetry/telemetry/value/string.py
@@ -9,14 +9,15 @@ from telemetry.value import none_values
 
 class StringValue(value_module.Value):
   def __init__(self, page, name, units, value, important=True,
-               description=None, none_value_reason=None):
+               description=None, none_value_reason=None, paths=None):
     """A single value (float, integer or string) result from a test.
 
     A test that output a hash of the content in a page might produce a
     string value:
        StringValue(page, 'page_hash', 'hash', '74E377FF')
     """
-    super(StringValue, self).__init__(page, name, units, important, description)
+    super(StringValue, self).__init__(page, name, units, important, description,
+                                      paths)
     assert value is None or isinstance(value, basestring)
     none_values.ValidateNoneValueReason(value, none_value_reason)
     self.value = value
@@ -27,13 +28,15 @@ class StringValue(value_module.Value):
       page_name = self.page.url
     else:
       page_name = None
-    return 'StringValue(%s, %s, %s, %s, important=%s, description=%s)' % (
+    return ('StringValue(%s, %s, %s, %s, important=%s, description=%s, '
+           'paths=%s)') % (
       page_name,
       self.name,
       self.units,
       self.value,
       self.important,
-      self.description)
+      self.description,
+      self.paths)
 
   def GetBuildbotDataType(self, output_context):
     if self._IsImportantGivenOutputIntent(output_context):