Make indexeddb save after the first sync

Save the sync data to indexeddb after the first catch-up

Fixes https://github.com/vector-im/riot-web/issues/3527

src/store/indexeddb.js

@@ -89,7 +89,7 @@ const IndexedDBStore = function IndexedDBStore(opts) {
     }
 
     this.startedUp = false;
-    this._syncTs = Date.now(); // updated when writes to the database are performed
+    this._syncTs = 0;
 
     // Records the last-modified-time of each user at the last point we saved
     // the database, such that we can derive the set if users that have been
@@ -123,7 +123,6 @@ IndexedDBStore.prototype.startup = function() {
             this._userModifiedMap[u.userId] = u.getLastModifiedTime();
             this.storeUser(u);
         });
-        this._syncTs = Date.now(); // pretend we've written so we don't rewrite
     });
 };
 
@@ -157,6 +156,12 @@ IndexedDBStore.prototype.deleteAllData = function() {
 IndexedDBStore.prototype.save = function() {
     const now = Date.now();
     if (now - this._syncTs > WRITE_DELAY_MS) {
+        return this._reallySave();
+    }
+    return q();
+};
+
+IndexedDBStore.prototype._reallySave = function() {
     this._syncTs = Date.now(); // set now to guard against multi-writes
 
     // work out changed users (this doesn't handle deletions but you
@@ -175,8 +180,6 @@ IndexedDBStore.prototype.save = function() {
     return this.backend.syncToDatabase(userTuples).catch((err) => {
         console.error("sync fail:", err);
     });
-    }
-    return q();
 };
 
 IndexedDBStore.prototype.setSyncData = function(syncData) {

src/sync.js

@@ -620,11 +620,13 @@ SyncApi.prototype._sync = function(syncOptions) {
         // keep emitting SYNCING -> SYNCING for clients who want to do bulk updates
         if (!isCachedResponse) {
             self._updateSyncState("SYNCING", syncEventData);
-        }
 
             // tell databases that everything is now in a consistent state and can be
-        // saved.
+            // saved (no point doing so if we only have the data we just got out of the
+            // store).
             client.store.save();
+        }
+
 
         // Begin next sync
         self._sync(syncOptions);