[Telemetry] Update all WPR json files to the new format.

tools/perf/page_sets/data/top_7_stress.json

 {
-    "description": "Describes the Web Page Replay archives for a user story set. Don't edit by hand! Use record_wpr for updating.", 
     "archives": {
-        "top_7_stress_004.wpr": [
-            "Facebook"
-        ], 
-        "top_7_stress_001.wpr": [
-            "https://plus.google.com/110031535020051778989/posts"
-        ], 
-        "top_7_stress_000.wpr": [
-            "https://www.google.com/#hl=en&q=barack+obama", 
-            "https://mail.google.com/mail/", 
-            "https://www.google.com/calendar/"
-        ], 
-        "top_7_stress_002.wpr": [
-            "Blogger", 
-            "Wordpress"
-        ]
-    }
+        "Blogger": {
+            "DEFAULT": "top_7_stress_002.wpr"
+        },
+        "Facebook": {
+            "DEFAULT": "top_7_stress_004.wpr"
+        },
+        "Wordpress": {
+            "DEFAULT": "top_7_stress_002.wpr"
+        },
+        "https://mail.google.com/mail/": {
+            "DEFAULT": "top_7_stress_000.wpr"
+        },
+        "https://plus.google.com/110031535020051778989/posts": {
+            "DEFAULT": "top_7_stress_001.wpr"
+        },
+        "https://www.google.com/#hl=en&q=barack+obama": {
+            "DEFAULT": "top_7_stress_000.wpr"
+        },
+        "https://www.google.com/calendar/": {
+            "DEFAULT": "top_7_stress_000.wpr"
+        }
+    },
+    "description": "Describes the Web Page Replay archives for a story set. Don't edit by hand! Use record_wpr for updating.",
+    "platform_specific": true
 }