[system health] Add media browsing stories.

tools/perf/page_sets/data/system_health_mobile.json

Index: tools/perf/page_sets/data/system_health_mobile.json
diff --git a/tools/perf/page_sets/data/system_health_mobile.json b/tools/perf/page_sets/data/system_health_mobile.json
index 503504ae0c247c0dd27879e26b9e3be5c7709be5..4d369f505196175d938e1cad462ccbd81f78b187 100644
--- a/tools/perf/page_sets/data/system_health_mobile.json
+++ b/tools/perf/page_sets/data/system_health_mobile.json
@@ -94,7 +94,17 @@
         ],
         "system_health_mobile_028.wpr": [
             "browse:social:facebook"
+        ],
+        "system_health_mobile_035.wpr": [
+            "browse:media:imgur",
+            "load:media:imgur"
+        ],
+        "system_health_mobile_037.wpr": [
+            "browse:media:youtube"
+        ],
+        "system_health_mobile_038.wpr": [
+            "browse:media:facebookphotos"
         ]
     },
     "description": "Describes the Web Page Replay archives for a story set. Don't edit by hand! Use record_wpr for updating."
-}
+}