Add new multipage_skpicture_printer benchmark and measurement

tools/perf/measurements/multipage_skpicture_printer.py

-# Copyright 2012 The Chromium Authors. All rights reserved.
+# Copyright 2016 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 legacy_page_test
-from telemetry.value import scalar
 
 
-_JS = 'chrome.gpuBenchmarking.printToSkPicture("{0}");'
+_JS = 'chrome.gpuBenchmarking.printPagesToSkPictures("{0}");'
 
 
-class SkpicturePrinter(legacy_page_test.LegacyPageTest):
+class MultipageSkpicturePrinter(legacy_page_test.LegacyPageTest):
 
-  def __init__(self, skp_outdir):
-    super(SkpicturePrinter, self).__init__()
-    self._skp_outdir = skp_outdir
+  def __init__(self, mskp_outdir):
+    super(MultipageSkpicturePrinter, self).__init__()
+    self._mskp_outdir = mskp_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 legacy_page_test.MeasurementFailure(
-          'SkPicture printing not supported on this platform')
+          'Multipage 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))
+        os.path.join(self._mskp_outdir, page.file_safe_name + '.mskp'))
     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)))