[telemetry] Make single-benchmark measurements protected and undiscoverable.

tools/perf/benchmarks/canvasmark.py

 # Copyright 2013 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.
 
 """Runs Canvasmark HTML5, Canvas 2D rendering and javascript benchmark.
 
 CanvasMark tests the HTML5 <canvas> rendering performance for commonly used
 operations in HTML5 games: bitmaps, canvas drawing, alpha blending, polygon
 fills, shadows and text functions.
 """
 
 import os
 
 from telemetry import test
 from telemetry.page import page_measurement
 from telemetry.page import page_set
 
-class CanvasMarkMeasurement(page_measurement.PageMeasurement):
+class _CanvasMarkMeasurement(page_measurement.PageMeasurement):
 
   def WillNavigateToPage(self, page, tab):
     page.script_to_evaluate_on_commit = """
         var __results = [];
         var __real_log = window.console.log;
         window.console.log = function(msg) {
           __results.push(msg);
           __real_log.apply(this, [msg]);
         }
         """
@@ skipping 10 matching lines @@
         'Unexpected result format "%s"' % score_and_name
       score = int(score_and_name[0])
       name = score_and_name[1][:-1]
       results.Add(name, 'score', score, data_type='unimportant')
       # Aggregate total score for all tests.
       total += score
     results.Add('Score', 'score', total)
 
 
 class CanvasMark(test.Test):
-  test = CanvasMarkMeasurement
+  test = _CanvasMarkMeasurement
 
   def CreatePageSet(self, options):
     return page_set.PageSet.FromDict({
         'archive_data_file': '../page_sets/data/canvasmark.json',
         'make_javascript_deterministic': False,
         'pages': [
           { 'url':
             'http://www.kevs3d.co.uk/dev/canvasmark/?auto=true'}
           ]
         }, os.path.abspath(__file__))