[Cleanup] Remove Screenshot measurement test from telemetry

tools/perf/measurements/screenshot.py

-# Copyright 2014 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
-
-from telemetry.image_processing import image_util
-from telemetry.page import page_test
-from telemetry.page import page_test
-from telemetry.value import scalar
-
-
-class Screenshot(page_test.PageTest):
-  def __init__(self, png_outdir):
-    super(Screenshot, self).__init__(
-        action_name_to_run = 'RunPageInteractions',
-        is_action_name_to_run_optional=True)
-    self._png_outdir = png_outdir
-
-  def ValidateAndMeasurePage(self, page, tab, results):
-    if not tab.screenshot_supported:
-      raise page_test.TestNotSupportedOnPlatformError(
-          'Browser does not support screenshotting')
-
-    tab.WaitForDocumentReadyStateToBeComplete()
-    screenshot = tab.Screenshot(60)
-
-    outpath = os.path.abspath(
-        os.path.join(self._png_outdir, page.file_safe_name)) + '.png'
-
-    if os.path.exists(outpath):
-      previous_mtime = os.path.getmtime(outpath)
-    else:
-      previous_mtime = -1
-
-    image_util.WritePngFile(screenshot, outpath)
-
-    saved_picture_count = 0
-    if os.path.exists(outpath) and os.path.getmtime(outpath) > previous_mtime:
-      saved_picture_count = 1
-    results.AddValue(scalar.ScalarValue(
-        results.current_page, 'saved_picture_count', 'count',
-        saved_picture_count))