Added some comments and a warning message to pyauto perf tests in perf.py.

chrome/test/functional/perf.py

Index: chrome/test/functional/perf.py
diff --git a/chrome/test/functional/perf.py b/chrome/test/functional/perf.py
index b23b9ee217e6eeed4ee7e9c2d03a4a403bd62f1a..8e572617775ebb5e94dac3972be34fc2e8364cf3 100644
--- a/chrome/test/functional/perf.py
+++ b/chrome/test/functional/perf.py
@@ -112,19 +112,33 @@ class BasePerfTest(pyauto.PyUITest):
   def _OutputPerfGraphValue(self, description, value):
     """Outputs a performance value to have it graphed on the performance bots.
 
-    Only used for ChromeOS.
+    Only used for ChromeOS.  The performance bots have a 30-character limit on
+    the length of the description for a performance value.  Any characters
+    beyond that are truncated before results are stored in the autotest
+    database.
 
     Args:
-      description: A string description of the performance value.
+      description: A string description of the performance value.  This will
+                   be truncated to 30 characters when stored in the autotest
+                   database.
       value: A numeric value representing a single performance measurement.
     """
     if self.IsChromeOS():
+      if len(description) > 30:
+        logging.warning('The description "%s" will be truncated to "%s" '
+                        '(length 30) when added to the autotest database.' %

[truty, 2011/10/20 00:12:01]

Not a big deal, but I think it's preferred when calling logging.xxxx() to avoid
the % string substitution and simple append arguments i.e. logging.warning('blah
%s more %s.', sub1, sub2)

[dennis_jeffrey, 2011/10/20 01:18:21]

Done (also changed in several other places in this file where the same comment
applies).

+                        (description, description[:30]))
       print '\n%s(\'%s\', %.2f)%s' % (self._PERF_OUTPUT_MARKER_PRE, description,
                                       value, self._PERF_OUTPUT_MARKER_POST)
 
   def _PrintSummaryResults(self, description, values, units):
     """Logs summary measurement information.
 
+    This function computes and outputs the average and standard deviation of
+    the specified list of value measurements.  It also invokes
+    _OutputPerfGraphValue() with the computed *average* value, to ensure the
+    average value can be plotted in a performance graph.
+
     Args:
       description: A string description for the specified results.
       values: A list of numeric value measurements.