Bug 1119061 - Part 1: Add Fennec-specific Sync 1.1 -> Sync 1.5 migration telemetry histograms. r=rnewman

The exponential histogram
FENNEC_SYNC11_MIGRATION_NOTIFICATIONS_OFFERED is triggered every time
the Android device tries to sync from the Sync11Migrated state.
Therefore, the notification offered may be (transparently) replacing
an existing notification; it doesn't necessarily mean we're nagging
the user after dismissal.

--HG--
extra : rebase_source : 6bb6b400ccedfef88b48a4ecc96269808a72fd07

toolkit/components/telemetry/Histograms.json

@@ -7157,5 +7157,32 @@
     "n_buckets" : 50,
     "extended_statistics_ok": true,
     "description": "The number of saved signons in storage"
+  },
+  "FENNEC_SYNC11_MIGRATION_SENTINELS_SEEN": {
+    "expires_in_version": "45",
+    "kind": "count",
+    "description": "The number of Sync 1.1 -> Sync 1.5 migration sentinels seen by Android Sync."
+  },
+  "FENNEC_SYNC11_MIGRATIONS_FAILED": {
+    "expires_in_version": "45",
+    "kind": "count",
+    "description": "The number of Sync 1.1 -> Sync 1.5 migrations that failed during Android Sync."
+  },
+  "FENNEC_SYNC11_MIGRATIONS_SUCCEEDED": {
+    "expires_in_version": "45",
+    "kind": "count",
+    "description": "The number of Sync 1.1 -> Sync 1.5 migrations that succeeded during Android Sync."
+  },
+  "FENNEC_SYNC11_MIGRATION_NOTIFICATIONS_OFFERED": {
+    "expires_in_version": "45",
+    "kind": "exponential",
+    "high": 500,
+    "n_buckets": 5,
+    "description": "The number of Sync 1.5 'complete upgrade/migration' notifications offered by Android Sync."
+  },
+  "FENNEC_SYNC11_MIGRATIONS_COMPLETED": {
+    "expires_in_version": "45",
+    "kind": "count",
+    "description": "The number of Sync 1.5 migrations completed by Android Sync."
   }
 }