hide lazy loading behind feature flag

src/MatrixClientPeg.js

@@ -107,7 +107,9 @@ class MatrixClientPeg {
         // the react sdk doesn't work without this, so don't allow
         opts.pendingEventOrdering = "detached";
 
-        opts.filter = await this.matrixClient.createFilter(FILTER_CONTENT);
+        if (SettingsStore.isFeatureEnabled('feature_lazyloading')) {
+            opts.filter = await this.matrixClient.createFilter(FILTER_CONTENT);
+        }
 
         try {
             const promise = this.matrixClient.store.startup();

src/components/structures/RoomView.js

@@ -314,7 +314,11 @@ module.exports = React.createClass({
                 this.setState({isPeeking: false});
 
                 //viewing a previously joined room, try to lazy load members
-                MatrixClientPeg.get().loadRoomMembersIfNeeded(room.roomId);
+
+                // lazy load members if enabled
+                if (SettingsStore.isFeatureEnabled('feature_lazyloading')) {
+                    MatrixClientPeg.get().loadRoomMembersIfNeeded(room.roomId);
+                }
             }
         }
     },

src/settings/Settings.js

@@ -83,6 +83,11 @@ export const SETTINGS = {
         supportedLevels: LEVELS_FEATURE,
         default: false,
     },
+    "feature_lazyloading": {
+        isFeature: true,
+        displayName: _td("Increase performance by loading room members on first view"),
+        supportedLevels: LEVELS_FEATURE,
+    },
     "MessageComposerInput.dontSuggestEmoji": {
         supportedLevels: LEVELS_ACCOUNT_SETTINGS,
         displayName: _td('Disable Emoji suggestions while typing'),