Make indexeddb startup faster

Don't needlessly transfer data from the worker to the main script
only to immediately transfer it right back again.

src/store/indexeddb-local-backend.js

@@ -136,6 +136,24 @@ LocalIndexedDBStoreBackend.prototype = {
         });
     },
 
+    /**
+     * Having connected, load initial data from the database and prepare for use
+     */
+    init: function() {
+        return q.all([
+            this._loadAccountData(),
+            this._loadSyncData(),
+        ]).then(([accountData, syncData]) => {
+            this._syncAccumulator.accumulate({
+                next_batch: syncData.nextBatch,
+                rooms: syncData.roomsData,
+                account_data: {
+                    events: accountData,
+                },
+            });
+        });
+    },
+
     /**
      * Clear the entire database. This should be used when logging out of a client
      * to prevent mixing data between accounts.
@@ -250,7 +268,7 @@ LocalIndexedDBStoreBackend.prototype = {
      * sync.
      * @return {Promise<Object[]>} A list of presence events in their raw form.
      */
-    loadUserPresenceEvents: function() {
+    getUserPresenceEvents: function() {
         return q.try(() => {
             const txn = this.db.transaction(["users"], "readonly");
             const store = txn.objectStore("users");
@@ -264,7 +282,7 @@ LocalIndexedDBStoreBackend.prototype = {
      * Load all the account data events from the database. This is not cached.
      * @return {Promise<Object[]>} A list of raw global account events.
      */
-    loadAccountData: function() {
+    _loadAccountData: function() {
         return q.try(() => {
             const txn = this.db.transaction(["accountData"], "readonly");
             const store = txn.objectStore("accountData");
@@ -278,7 +296,7 @@ LocalIndexedDBStoreBackend.prototype = {
      * Load the sync data from the database.
      * @return {Promise<Object>} An object with "roomsData" and "nextBatch" keys.
      */
-    loadSyncData: function() {
+    _loadSyncData: function() {
         return q.try(() => {
             const txn = this.db.transaction(["sync"], "readonly");
             const store = txn.objectStore("sync");