Bug 1338812 - Call TelemetryStopwatch only once per item (history / bookmarks / logins) rather than for each resource. r=Gijs

MozReview-Commit-ID: 7c5DgKDIFTv

--HG--
extra : rebase_source : 9141f895c95f31b682e047d7df203aed32e3d65b

browser/components/migration/MigrationUtils.jsm

@@ -249,16 +249,16 @@ this.MigratorPrototype = {
       }
       return null;
     };
-    let maybeStartTelemetryStopwatch = (resourceType, resource) => {
+    let maybeStartTelemetryStopwatch = (resourceType) => {
       let histogram = getHistogramForResourceType(resourceType);
       if (histogram) {
-        TelemetryStopwatch.startKeyed(histogram, this.getKey(), resource);
+        TelemetryStopwatch.startKeyed(histogram, this.getKey());
       }
     };
-    let maybeStopTelemetryStopwatch = (resourceType, resource) => {
+    let maybeStopTelemetryStopwatch = (resourceType) => {
       let histogram = getHistogramForResourceType(resourceType);
       if (histogram) {
-        TelemetryStopwatch.finishKeyed(histogram, this.getKey(), resource);
+        TelemetryStopwatch.finishKeyed(histogram, this.getKey());
       }
     };
 
@@ -297,12 +297,12 @@ this.MigratorPrototype = {
       for (let [migrationType, itemResources] of resourcesGroupedByItems) {
         notify("Migration:ItemBeforeMigrate", migrationType);
 
+        maybeStartTelemetryStopwatch(migrationType);
+
         let itemSuccess = false;
         for (let res of itemResources) {
-          maybeStartTelemetryStopwatch(migrationType, res);
           let completeDeferred = PromiseUtils.defer();
           let resourceDone = function(aSuccess) {
-            maybeStopTelemetryStopwatch(migrationType, res);
             itemResources.delete(res);
             itemSuccess |= aSuccess;
             if (itemResources.size == 0) {
@@ -310,6 +310,9 @@ this.MigratorPrototype = {
                      "Migration:ItemAfterMigrate" : "Migration:ItemError",
                      migrationType);
               resourcesGroupedByItems.delete(migrationType);
+
+              maybeStopTelemetryStopwatch(migrationType);
+
               if (resourcesGroupedByItems.size == 0) {
                 collectQuantityTelemetry();
                 notify("Migration:Ended");