[Telemetry] Set youtube system health benchmarks to have platform specific recordings.

tools/perf/page_sets/system_health/loading_stories.py

 # 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.
 
 from page_sets.system_health import platforms
 from page_sets.system_health import system_health_story
 
 from page_sets.login_helpers import dropbox_login
 from page_sets.login_helpers import google_login
 
@@ skipping 190 matching lines @@
 
 ################################################################################
 # Audio, images, and video.
 ################################################################################
 
 
 class LoadYouTubeStory(_LoadingStory):
   # No way to disable autoplay on desktop.
   NAME = 'load:media:youtube'
   URL = 'https://www.youtube.com/watch?v=QGfhS1hfTWw&autoplay=false'
+  PLATFORM_SPECIFIC = True
 
 
 class LoadDailymotionStory(_LoadingStory):
   # The side panel with related videos doesn't show on desktop due to
   # https://github.com/chromium/web-page-replay/issues/74.
   NAME = 'load:media:dailymotion'
   URL = (
       'https://www.dailymotion.com/video/x489k7d_street-performer-shows-off-slinky-skills_fun?autoplay=false')
 
 
@@ skipping 170 matching lines @@
   NAME = 'load:games:miniclip'
   # Using "https://" causes "404 Not Found" during WPR recording.
   URL = 'http://www.miniclip.com/games/en/'
   SUPPORTED_PLATFORMS = platforms.DESKTOP_ONLY  # Requires Flash.
 
 
 class LoadAlphabettyStory(_LoadingStory):
   NAME = 'load:games:alphabetty'
   URL = 'https://king.com/play/alphabetty'
   SUPPORTED_PLATFORMS = platforms.DESKTOP_ONLY  # Requires Flash.