[perf] Add load:news:hackernews:2018 system health story

Bug: 878390
Change-Id: If95d9fc73619e626e4e82189a63284706a664ffb
Reviewed-on: https://chromium-review.googlesource.com/c/1264586Reviewed-by: Juan Antonio Navarro Pérez <perezju@chromium.org>
Commit-Queue: Ulan Degenbaev <ulan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#597526}

tools/perf/page_sets/data/system_health_desktop.json

@@ -150,6 +150,9 @@
         "load:news:hackernews": {
             "DEFAULT": "system_health_desktop_008.wprgo"
         },
+        "load:news:hackernews:2018": {
+            "DEFAULT": "system_health_desktop_fd099ca6a6.wprgo"
+        },
         "load:news:nytimes": {
             "DEFAULT": "system_health_desktop_009.wprgo"
         },

tools/perf/page_sets/data/system_health_desktop_fd099ca6a6.wprgo.sha1

+fd099ca6a617e7257a045c64acafec5f74dc778b
\ No newline at end of file

tools/perf/page_sets/system_health/loading_stories.py

@@ -170,6 +170,13 @@ class LoadHackerNewsDesktopStory(_LoadingStory):
   SUPPORTED_PLATFORMS = platforms.DESKTOP_ONLY
 
 
+class LoadHackerNewsDesktopStory2018(_LoadingStory):
+  NAME = 'load:news:hackernews:2018'
+  URL = 'https://news.ycombinator.com'
+  TAGS = [story_tags.YEAR_2018]
+  SUPPORTED_PLATFORMS = platforms.DESKTOP_ONLY
+
+
 class LoadNytimesDesktopStory(_LoadingStory):
   NAME = 'load:news:nytimes'
   URL = 'http://www.nytimes.com'