merge upstream changes

services/sync/modules/engines.js

@@ -101,6 +101,8 @@ Engine.prototype = {
   // "user-data/default-engine/";
   get serverPrefix() { throw "serverPrefix property must be overridden in subclasses"; },
 
+  get snapshot() this._snapshot,
+
   get _remote() {
     if (!this.__remote)
       this.__remote = new RemoteStore(this.serverPrefix, 'Engine:' + this.name);

services/sync/modules/service.js

@@ -209,7 +209,7 @@ WeaveSvc.prototype = {
     this._scheduleTimer = Cc["@mozilla.org/timer;1"].
       createInstance(Ci.nsITimer);
     let listener = new Utils.EventListener(Utils.bind2(this, this._onSchedule));
-    this._scheduleTimer.initWithCallback(listener, 1800000, // 30 min
+    this._scheduleTimer.initWithCallback(listener, 120000, // 2 min
                                          this._scheduleTimer.TYPE_REPEATING_SLACK);
     this._log.info("Weave scheduler enabled");
   },
@@ -506,7 +506,7 @@ WeaveSvc.prototype = {
 
     let engines = Engines.getAll();
     for (let i = 0; i < engines.length; i++) {
-      if (engines[i].enabled) {
+      if (engines[i].enabled && engines[i]._tracker.score >= 30) {
         this._notify(engines[i].name + "-engine:sync",
                      this._syncEngine, engines[i]).async(this, self.cb);
         yield;
@@ -522,6 +522,8 @@ WeaveSvc.prototype = {
     try {
       engine.sync(self.cb);
       yield;
+      engine._tracker.resetScore();
+      yield;
     } catch(e) {
       this._log.error(Utils.exceptionStr(e));
       if (e.trace)