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

tools/perf/page_sets/data/kraken.json

Index: tools/perf/page_sets/data/kraken.json
diff --git a/tools/perf/page_sets/data/kraken.json b/tools/perf/page_sets/data/kraken.json
index a2cd25f9368d89f4efa4687cedecf0760279b795..a9b1d44d5a5570d1368b25f8427a385dbdc590df 100644
--- a/tools/perf/page_sets/data/kraken.json
+++ b/tools/perf/page_sets/data/kraken.json
@@ -1,8 +1,9 @@
 {
-    "description": "Describes the Web Page Replay archives for a page set. Don't edit by hand! Use record_wpr for updating.",
     "archives": {
-        "kraken_000.wpr" : [
-            "http://krakenbenchmark.mozilla.org/kraken-1.1/driver.html"
-        ]
-    }
-}
+        "http://krakenbenchmark.mozilla.org/kraken-1.1/driver.html": {
+            "DEFAULT": "kraken_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
+}