Bug 1057386 - Provide an API to let the shutdown leak detector wait until resources are properly destroyed r=adw

browser/modules/ContentSearch.jsm

@@ -87,21 +87,30 @@ this.ContentSearch = {
   // { controller, previousFormHistoryResult }.  See _onMessageGetSuggestions.
   _suggestionMap: new WeakMap(),
 
+  // Resolved when we finish shutting down.
+  _destroyedPromise: null,
+
   init: function () {
     Cc["@mozilla.org/globalmessagemanager;1"].
       getService(Ci.nsIMessageListenerManager).
       addMessageListener(INBOUND_MESSAGE, this);
     Services.obs.addObserver(this, "browser-search-engine-modified", false);
+    Services.obs.addObserver(this, "shutdown-leaks-before-check", false);
   },
 
   destroy: function () {
+    if (this._destroyedPromise) {
+      return this._destroyedPromise;
+    }
+
     Cc["@mozilla.org/globalmessagemanager;1"].
       getService(Ci.nsIMessageListenerManager).
       removeMessageListener(INBOUND_MESSAGE, this);
     Services.obs.removeObserver(this, "browser-search-engine-modified");
+    Services.obs.removeObserver(this, "shutdown-leaks-before-check");
 
     this._eventQueue.length = 0;
-    return Promise.resolve(this._currentEventPromise);
+    return this._destroyedPromise = Promise.resolve(this._currentEventPromise);
   },
 
   /**
@@ -148,6 +157,10 @@ this.ContentSearch = {
       });
       this._processEventQueue();
       break;
+    case "shutdown-leaks-before-check":
+      subj.wrappedJSObject.client.addBlocker(
+        "ContentSearch: Wait until the service is destroyed", () => this.destroy());
+      break;
     }
   },
 

testing/mochitest/browser-test.js

@@ -458,7 +458,6 @@ Tester.prototype = {
     // is invoked to start the tests.
     this.waitForWindowsState((function () {
       if (this.done) {
-        let promise = Promise.resolve();
 
         // Uninitialize a few things explicitly so that they can clean up
         // frames and browser intentionally kept alive until shutdown to
@@ -489,15 +488,8 @@ Tester.prototype = {
           SocialFlyout.unload();
           SocialShare.uninit();
           TabView.uninit();
-
-          // Destroying ContentSearch is asynchronous.
-          promise = ContentSearch.destroy();
         }
 
-        // Simulate memory pressure so that we're forced to free more resources
-        // and thus get rid of more false leaks like already terminated workers.
-        Services.obs.notifyObservers(null, "memory-pressure", "heap-minimize");
-
         // Schedule GC and CC runs before finishing in order to detect
         // DOM windows leaked by our tests or the tested code. Note that we
         // use a shrinking GC so that the JS engine will discard JIT code and
@@ -527,7 +519,19 @@ Tester.prototype = {
           }
         };
 
-        promise.then(() => {
+        let {AsyncShutdown} =
+          Cu.import("resource://gre/modules/AsyncShutdown.jsm", {});
+
+        let barrier = new AsyncShutdown.Barrier(
+          "ShutdownLeaks: Wait for cleanup to be finished before checking for leaks");
+        Services.obs.notifyObservers({wrappedJSObject: barrier},
+          "shutdown-leaks-before-check", null);
+
+        barrier.wait().then(() => {
+          // Simulate memory pressure so that we're forced to free more resources
+          // and thus get rid of more false leaks like already terminated workers.
+          Services.obs.notifyObservers(null, "memory-pressure", "heap-minimize");
+
           checkForLeakedGlobalWindows(aResults => {
             if (aResults.length == 0) {
               this.finish();