telemetry: Allow page tests to be configured via constructor

tools/perf/measurements/skpicture_printer.py

 # Copyright 2012 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.
 import glob
 import os
 
 from telemetry.page import page_test
 from telemetry.value import scalar
 
 
 _JS = 'chrome.gpuBenchmarking.printToSkPicture("{0}");'
 
 
 class SkpicturePrinter(page_test.PageTest):
-  @classmethod
-  def AddCommandLineArgs(cls, parser):
+  def __init__(self):
+    super(SkpicturePrinter, self).__init__()
+    self._skp_outdir = None
+
+  def AddCommandLineArgs(self, parser):
     parser.add_option('-s', '--skp-outdir',
                       help='Output directory for the SKP files')
 
-  @classmethod
-  def ProcessCommandLineArgs(cls, parser, args):
+  def ProcessCommandLineArgs(self, parser, args):
     if not args.skp_outdir:
       parser.error('Please specify --skp-outdir')
-    cls._skp_outdir = args.skp_outdir
+    self._skp_outdir = args.skp_outdir
 
   def CustomizeBrowserOptions(self, options):
     options.AppendExtraBrowserArgs(['--enable-gpu-benchmarking',
                                     '--no-sandbox',
                                     '--enable-deferred-image-decoding'])
 
   def ValidateAndMeasurePage(self, page, tab, results):
     if tab.browser.platform.GetOSName() in ['android', 'chromeos']:
       raise page_test.MeasurementFailure(
           'SkPicture printing not supported on this platform')
 
     # Replace win32 path separator char '\' with '\\'.
     outpath = os.path.abspath(
         os.path.join(self._skp_outdir, page.file_safe_name))
     js = _JS.format(outpath.replace('\\', '\\\\'))
     tab.EvaluateJavaScript(js)
     pictures = glob.glob(os.path.join(outpath, '*.skp'))
     results.AddValue(scalar.ScalarValue(
         results.current_page, 'saved_picture_count', 'count', len(pictures)))