Bug 1358907 Part 2 Wait for database load before shutting down r=mossop

Make sure the XPI database is fully loaded before running the
XPIDatabase.shutdown() logic.  This race has been present for a long
time but it suddenly became much more common when loading of the XPI
database was deferred until after startup.

MozReview-Commit-ID: 1llKuH3It19

--HG--
extra : rebase_source : de18515e0c38193d70953a49803fadb43be9286c

toolkit/mozapps/extensions/internal/XPIProviderUtils.js

@@ -658,7 +658,7 @@ this.XPIDatabase = {
    *                          flush after the database is flushed and
    *                          all cleanup is done
    */
-  shutdown() {
+  async shutdown() {
     logger.debug("shutdown");
     if (this.initialized) {
       // If our last database I/O had an error, try one last time to save.
@@ -676,17 +676,25 @@ this.XPIDatabase = {
             "XPIDB_saves_late", this._deferredSave.dirty ? 1 : 0);
       }
 
-      // Return a promise that any pending writes of the DB are complete and we
-      // are finished cleaning up
-      let flushPromise = this.flush();
-      flushPromise.catch(error => {
+      // If we're shutting down while still loading, finish loading
+      // before everything else!
+      if (this._dbPromise) {
+        await this._dbPromise;
+      }
+
+      // Await and pending DB writes and finish cleaning up.
+      try {
+        await this.flush();
+      } catch (error) {
         logger.error("Flush of XPI database failed", error);
         AddonManagerPrivate.recordSimpleMeasure("XPIDB_shutdownFlush_failed", 1);
         // If our last attempt to read or write the DB failed, force a new
         // extensions.ini to be written to disk on the next startup
         Services.prefs.setBoolPref(PREF_PENDING_OPERATIONS, true);
-        })
-        .then(count => {
+
+        throw error;
+      }
+
       // Clear out the cached addons data loaded from JSON
       delete this.addonDB;
       delete this._dbPromise;
@@ -694,10 +702,7 @@ this.XPIDatabase = {
       delete this._deferredSave;
       // re-enable the schema version setter
       delete this._schemaVersionSet;
-        });
-      return flushPromise;
     }
-    return Promise.resolve(0);
   },
 
   /**

toolkit/mozapps/extensions/test/xpcshell/test_corrupt.js

@@ -255,6 +255,15 @@ function run_test_1() {
     gExtensionsJSON.create(AM_Ci.nsIFile.DIRECTORY_TYPE, FileUtils.PERMS_DIRECTORY);
     startupManager(false);
 
+    // Load the database.
+    awaitPromise(new Promise(resolve => {
+      Services.obs.addObserver(function listener() {
+        Services.obs.removeObserver(listener, "xpi-database-loaded");
+        resolve();
+      }, "xpi-database-loaded");
+      Services.obs.notifyObservers(null, "sessionstore-windows-restored");
+    }));
+
     // Accessing the add-ons should open and recover the database
     AddonManager.getAddonsByIDs(["addon1@tests.mozilla.org",
                                  "addon2@tests.mozilla.org",