Bug 1313960 - synchronous addon DB loader should handle in-progress async load r=kmag

MozReview-Commit-ID: LwzmRr3PdXx

--HG--
extra : rebase_source : d8c8aa7c3974fe88f4b6228a157dc3140c664980

toolkit/mozapps/extensions/internal/XPIProviderUtils.js

@@ -619,14 +619,11 @@ this.XPIDatabase = {
       if (fstream)
         fstream.close();
     }
-    // If an async load was also in progress, resolve that promise with our DB;
-    // otherwise create a resolved promise
+    // If an async load was also in progress, record in telemetry.
     if (this._dbPromise) {
       AddonManagerPrivate.recordSimpleMeasure("XPIDB_overlapped_load", 1);
-      this._dbPromise.resolve(this.addonDB);
     }
-    else
-      this._dbPromise = Promise.resolve(this.addonDB);
+    this._dbPromise = Promise.resolve(this.addonDB);
   },
 
   /**
@@ -770,7 +767,8 @@ this.XPIDatabase = {
         logger.debug("Async JSON file read took " + readOptions.outExecutionDuration + " MS");
         AddonManagerPrivate.recordSimpleMeasure("XPIDB_asyncRead_MS",
           readOptions.outExecutionDuration);
-        if (this._addonDB) {
+
+        if (this.addonDB) {
           logger.debug("Synchronous load completed while waiting for async load");
           return this.addonDB;
         }
@@ -782,9 +780,9 @@ this.XPIDatabase = {
         this.parseDB(data, true);
         return this.addonDB;
       })
-    .then(null,
+    .catch(
       error => {
-        if (this._addonDB) {
+        if (this.addonDB) {
           logger.debug("Synchronous load completed while waiting for async load");
           return this.addonDB;
         }