Reland "Mark some WebRTC perf measurements as biggerIsBetter"

This is a reland of 9c270678

Fixed invalid unit and improved the error message for an invalid unit.

`./tools/perf/run_benchmark run webrtc --browser=system` passes locally
on Mac.

Original change's description:
> Mark some WebRTC perf measurements as biggerIsBetter
>
> Change-Id: I95a145f0380b0f413a71ef5a9bbacf840eb20b9f
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2577205
> Commit-Queue: John Chen <johnchen@chromium.org>
> Auto-Submit: Ben Wagner aka dogben <benjaminwagner@google.com>
> Reviewed-by: Mirko Bonadei <mbonadei@chromium.org>
> Reviewed-by: John Chen <johnchen@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#834889}

Change-Id: Id7220dafb11faab2cb3e28b36aed3c6a526575c5
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2580072Reviewed-by: Mirko Bonadei <mbonadei@chromium.org>
Reviewed-by: John Chen <johnchen@chromium.org>
Commit-Queue: John Chen <johnchen@chromium.org>
Auto-Submit: Ben Wagner aka dogben <benjaminwagner@google.com>
Cr-Commit-Position: refs/heads/master@{#835200}

tools/perf/core/results_processor/processor.py

@@ -16,6 +16,7 @@ import json
 import logging
 import os
 import posixpath
+import pprint
 import random
 import re
 import shutil
@@ -406,7 +407,10 @@ def MeasurementToHistogram(name, measurement):
     unit = info.name
     samples = [s * info.conversion_factor for s in samples]
   if unit not in histogram.UNIT_NAMES:
-    raise ValueError('Unknown unit: %s' % unit)
+    raise ValueError(('Unknown unit: "%s". Valid options include:\n%s\n'
+                      'Valid legacy options include:\n%s') %
+                     (unit, pprint.pformat(histogram.UNIT_NAMES),
+                      pprint.pformat(legacy_unit_info.LEGACY_UNIT_INFO.keys())))
   return histogram.Histogram.Create(name, unit, samples,
                                     description=description)
 

tools/perf/page_sets/webrtc_cases.py

@@ -48,7 +48,7 @@ class DataChannel(WebrtcPage):
   def ParseTestResults(self, action_runner):
     self.AddJavaScriptMeasurement(
         'data_transferred',
-        'bytes',
+        'sizeInBytes_biggerIsBetter',
         'receiveProgress.value',
         description='Amount of data transferred by data channel in 10 seconds')
     self.AddJavaScriptMeasurement(
@@ -160,7 +160,7 @@ class InsertableStreamsVideoProcessing(WebrtcPage):
 
   def ExecuteTest(self, action_runner):
     self.AddMeasurement(
-        'supported', 'count', 1 if self.supported else 0,
+        'supported', 'count_biggerIsBetter', 1 if self.supported else 0,
         'Boolean flag indicating if this benchmark is supported by the browser.'
     )
     if not self.supported:
@@ -183,7 +183,7 @@ class InsertableStreamsVideoProcessing(WebrtcPage):
       action_runner.Wait(10)
     self.AddJavaScriptMeasurement(
         'sink_decoded_frames',
-        'count',
+        'count_biggerIsBetter',
         'document.querySelector(".sinkVideo").webkitDecodedFrameCount',
         description='Number of frames received at the sink video.')