diff --git a/dom/base/Webapps.jsm b/dom/base/Webapps.jsm
index 743f8801cfd7..e18230d7ec08 100644
--- a/dom/base/Webapps.jsm
+++ b/dom/base/Webapps.jsm
@@ -148,7 +148,7 @@ let DOMApplicationRegistry = {
         aCallbak();
     });
   },
-  
+
   // clones a app object, without the manifest
   _cloneAppObject: function(aApp) {
     let clone = {
@@ -159,14 +159,14 @@ let DOMApplicationRegistry = {
     };
     return clone;
   },
-  
+
   denyInstall: function(aData) {
     this.mm.sendAsyncMessage("Webapps:Install:Return:KO", aData);
   },
-  
-  confirmInstall: function(aData) {
+
+  confirmInstall: function(aData, aFromSync) {
     let app = aData.app;
-    let id = this._appId(app.origin);
+    let id = app.syncId || this._appId(app.origin);
 
     // install an application again is considered as an update
     if (id) {
@@ -191,11 +191,14 @@ let DOMApplicationRegistry = {
     delete this.webapps[id].manifest;
     this.webapps[id].installTime = (new Date()).getTime()
 
-    this._writeFile(this.appsFile, JSON.stringify(this.webapps), (function() {
-      this.mm.sendAsyncMessage("Webapps:Install:Return:OK", aData);
-    }).bind(this));
+    
+    if (!aFromSync)
+      this._saveApps((function() {
+        this.mm.sendAsyncMessage("Webapps:Install:Return:OK", aData);
+        Services.obs.notifyObservers(this, "webapps-sync-install", id);
+      }).bind(this));
   },
- 
+
   _appId: function(aURI) {
     for (let id in this.webapps) {
       if (this.webapps[id].origin == aURI)
@@ -204,6 +207,13 @@ let DOMApplicationRegistry = {
     return null;
   },
 
+  _saveApps: function(aCallback) {
+    this._writeFile(this.appsFile, JSON.stringify(this.webapps), function() {
+      if (aCallback)
+        aCallback();
+    });
+  },
+
   /**
     * Asynchronously reads a list of manifests
     */
@@ -219,23 +229,25 @@ let DOMApplicationRegistry = {
         this._readManifests(aData, aFinalCallback, index + 1);
     }).bind(this)); 
   },
- 
+
   uninstall: function(aData) {
     for (let id in this.webapps) {
       let app = this.webapps[id];
       if (app.origin == aData.origin) {
         delete this.webapps[id];
-        this._writeFile(this.appsFile, JSON.stringify(this.webapps));
         let dir = FileUtils.getDir("ProfD", ["webapps", id], true, true);
         try {
           dir.remove(true);
         } catch (e) {
         }
-        this.mm.sendAsyncMessage("Webapps:Uninstall:Return:OK", aData);
+        this._saveApps((function() {
+          this.mm.sendAsyncMessage("Webapps:Uninstall:Return:OK", aData);
+          Services.obs.notifyObservers(this, "webapps-sync-uninstall", id);
+        }).bind(this));
       }
     }
   },
-  
+
   enumerate: function(aData) {
     aData.apps = [];
     let tmp = [];
@@ -302,7 +314,6 @@ let DOMApplicationRegistry = {
       return;
 
     let id = this._appId(aOrigin);
-
     if (!id) {
       aCallback(null);
       return;
@@ -311,7 +322,76 @@ let DOMApplicationRegistry = {
     this._readManifests([{ id: id }], function(aResult) {
       aCallback(aResult[0].manifest);
     });
-  }
+  },
+
+  /** added to support the sync engine */
+
+  getAppById: function(aId) {
+    if (!this.webapps[aId])
+      return null;
+
+    let app = this._cloneAppObject(this.webapps[aId]);
+    return app;
+  },
+  
+  itemExists: function(aId) {
+    return !!this.webapps[aId];
+  },
+
+  updateApps: function(aRecords, aCallback) {
+    for (let i = 0; i < aRecords.length; i++) {
+      let record = aRecords[i];
+      if (record.deleted) {
+        if (!this.webapps[record.id])
+          continue;
+        let origin = this.webapps[record.id].origin;
+        delete this.webapps[record.id];
+        let dir = FileUtils.getDir("ProfD", ["webapps", record.id], true, true);
+        try {
+          dir.remove(true);
+        } catch (e) {
+        }
+        this.mm.sendAsyncMessage("Webapps:Uninstall:Return:OK", { origin: origin });
+      } else {
+        if (!!this.webapps[record.id]) {
+          this.webapps[record.id] = record.value;
+          delete this.webapps[record.id].manifest;
+        }
+        else {
+          let data = { app: record.value };
+          this.confirmInstall(data, true);
+          this.mm.sendAsyncMessage("Webapps:Install:Return:OK", data);
+        }
+      }
+    }
+    this._saveApps(aCallback);
+  },
+
+  /*
+   * May be removed once sync API change
+   */
+  getAllIDs: function() {
+    let apps = {};
+    for (let id in this.webapps) {
+      // only sync http and https apps
+      if (this.webapps[id].origin.indexOf("http") == 0)
+        apps[id] = true;
+    }
+    return apps;
+  },
+
+  wipe: function(aCallback) {
+    let ids = this.getAllIDs();
+    for (let id in ids) {
+      delete this.webapps[id];
+      let dir = FileUtils.getDir("ProfD", ["webapps", id], true, true);
+      try {
+        dir.remove(true);
+      } catch (e) {
+      }
+    }
+    this._saveApps(aCallback);
+   }
 };
 
 /**