Modify list_system_health_stories to generate_system_health_csv

tools/perf/generate_system_health_csv

 #!/usr/bin/env python
 # 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 csv
+import os
 import sys
 
 from core import path_util
 sys.path.insert(1, path_util.GetTelemetryDir())  # To resolve telemetry imports
 
 import page_sets
 
 
 def IterAllSystemHealthStories():
   for s in page_sets.SystemHealthStorySet(platform='desktop'):
     yield s
   for s in page_sets.SystemHealthStorySet(platform='mobile'):
     if len(s.SUPPORTED_PLATFORMS) < 2:
       yield s
 
+SYSTEM_HEALTH_CSV = os.path.join(os.path.dirname(__file__),
+                                 'system_health_stories.csv')
+
 
 def main():
   system_health_stories = list(IterAllSystemHealthStories())
   system_health_stories.sort(key=lambda s: s.name)
-  print '{0:60} {1}'.format('Story name', 'Supported platform')
-  print '-' * 79
-  for s in system_health_stories:
-    p = s.SUPPORTED_PLATFORMS
-    if len(p) == 2:
-      p = 'all'
-    else:
-      p = list(p)[0]
-    print '{0:60} {1}'.format(s.name, p)
+  with open(SYSTEM_HEALTH_CSV, 'w') as f:
+    csv_writer = csv.writer(f)
+    csv_writer.writerow([
+        'Story name', 'Platform', 'Description'])
+    for s in system_health_stories:
+      p = s.SUPPORTED_PLATFORMS
+      if len(p) == 2:
+        p = 'all'
+      else:
+        p = list(p)[0]
+      csv_writer.writerow([s.name, p, s.GetStoryDescription()])
   return 0
 
 
 if __name__ == '__main__':
   sys.exit(main())