Telemetry: Sanitize a key and add description to speedindex metrics

tools/perf/metrics/speedindex.py

Index: tools/perf/metrics/speedindex.py
diff --git a/tools/perf/metrics/speedindex.py b/tools/perf/metrics/speedindex.py
index bfd415842b103586fca0acef8ccddb5ba202d0d8..27d87c6f4223a17d3e8c31c9fbde50b3aa790da5 100644
--- a/tools/perf/metrics/speedindex.py
+++ b/tools/perf/metrics/speedindex.py
@@ -53,7 +53,16 @@ class SpeedIndexMetric(Metric):
     # Release the tab so that it can be disconnected.
     self._impl = None
     results.AddValue(scalar.ScalarValue(
-        results.current_page, '%s.speed_index' % chart_name, 'ms', index))
+        results.current_page, '%s_speed_index' % chart_name, 'ms', index,

[qyearsley, 2014/10/23 17:01:39]

This change from %s.speed_index to %s_speed_index was intentional, right?

[shimazu, 2014/10/27 02:33:12]

Yes, I saw the result of run_benchmark as 'yourChartName: speed_index' format
though 'yourChartName_speed_index: url' is our expectation. This is caused by
the dot, so I changed the dot to underscore.

+        description='Speed Index. This focuses on a time when visible parts of '

[qyearsley, 2014/10/23 17:01:39]

a time -> time

[shimazu, 2014/10/27 02:33:12]

Done.

+                    'page are displayed, and this shows the time when the '
+                    'first look is "almost" composed. If you want to get more '

[qyearsley, 2014/10/23 17:01:39]

I'm not sure if this description is accurate. Speed index doesn't indicate the
time when any particular event happened -- it's just supposed to be a measure of
load time when is lower when most of the page loads sooner.

[shimazu, 2014/10/27 02:33:11]

I tried to add such explanation. I'm not sure how detail I have to write. Is it
okay or a bit too redundant?

[qyearsley, 2014/10/27 02:55:46]

I personally think it might be a bit redundant, because that link
(http://goo.gl/Rw3d5d) has more details.

+                    'detail, please refer to http://goo.gl/Rw3d5d . Currently '

[qyearsley, 2014/10/23 17:01:39]

No need for the space between the URL and the dot.

[shimazu, 2014/10/27 02:33:12]

Done.

+                    'there are two implementation: for Android and for '

[qyearsley, 2014/10/23 17:01:39]

implementation -> implementations

[shimazu, 2014/10/27 02:33:11]

Done.

+                    'Desktop. Android version (using video capture) is good '
+                    'index to show the advantage of your patch, but Desktop '
+                    'one (using paint events) is not because of extra overhead '
+                    'to catch paint events.'))

[qyearsley, 2014/10/23 17:01:39]

I wouldn't say the desktop version is "not good", but it is worth noting that it
it has extra overhead.

I would phrase this sentence as:

"The Android version uses video capture; the Desktop one uses paint events and
has extra overhead to catch paint events.

[shimazu, 2014/10/27 02:33:12]

Done.

 
   def IsFinished(self, tab):
     """Decide whether the timeline recording should be stopped.