Implemented telemetry benchmark that loads page and outputs screenshot.

tools/perf/contrib/cluster_telemetry/screenshot_unittest.py

+# Copyright 2017 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 os
+import shutil
+import tempfile
+
+from telemetry import decorators
+from telemetry.testing import options_for_unittests
+from telemetry.testing import page_test_test_case
+from telemetry.util import image_util
+from contrib.cluster_telemetry import screenshot
+
+class ScreenshotUnitTest(page_test_test_case.PageTestTestCase):
+
+  def setUp(self):
+    self._options = options_for_unittests.GetCopy()
+    self._png_outdir = tempfile.mkdtemp('_png_test')
+
+  def tearDown(self):
+    shutil.rmtree(self._png_outdir)
+
+  @decorators.Enabled('linux')
+  def testScreenshot(self):
+    # Screenshots for Cluster Telemetry purposes currently only supported on
+    # Linux platform.
+    page_set = self.CreateStorySetFromFileInUnittestDataDir(
+      'screenshot_test.html')
+    measurement = screenshot.Screenshot(self._png_outdir)
+    self.RunMeasurement(measurement, page_set, options=self._options)
+
+    path = self._png_outdir + '/' + page_set.stories[0].file_safe_name + '.png'
+    self.assertTrue(os.path.exists(path))
+    self.assertTrue(os.path.isfile(path))
+    self.assertTrue(os.access(path, os.R_OK))
+
+    image = image_util.FromPngFile(path)
+    screenshot_pixels = image_util.Pixels(image)
+    special_colored_pixel = bytearray([217, 115, 43])
+    self.assertTrue(special_colored_pixel in screenshot_pixels)