Background

In a single-view world, the rasterization begins once the framework calls FlutterView.render. In a multi-view world, rasterization begins once the onDrawFrame callback exits. Thus, expensive work that happens after a FlutterView.render could cause end-to-end render performance to regress.

Solution

1. Investigate whether work that happens after FlutterView.render is expensive.
2. If it expensive, consider adding an optimization where we begin rasterization once FlutterView.render has been called on all views. This depends on: Ignore duplicate FlutterView.render calls in the same frame #144444