Bug 840643 - Fix exception in WeaveGlue.init that breaks Metro sync setup [r=ally]

browser/metro/base/content/sync.js

@@ -24,15 +24,10 @@ let WeaveGlue = {
 
     if (service.ready) {
       this._init();
-      return;
+    } else {
+      Services.obs.addObserver(this, "weave:service:ready", false);
+      service.ensureLoaded();
     }
-
-    Services.obs.addObserver(function onReady() {
-      Services.obs.removeObserver(onReady, "weave:service:ready");
-      this._init();
-    }.bind(this), "weave:service:ready", false);
-
-    service.ensureLoaded();
   },
 
   _init: function () {
@@ -425,6 +420,12 @@ let WeaveGlue = {
   },
 
   observe: function observe(aSubject, aTopic, aData) {
+    if (aTopic == "weave:service:ready") {
+      Services.obs.removeObserver(this, aTopic);
+      this._init();
+      return;
+    }
+
     // Make sure we're online when connecting/syncing
     Util.forceOnline();