31cde4f8d3
This enhances the overlay optimization by delaying combining pictures to get tighter bounds for the pictures that make up the scene, enabling more sophisticated optimization since we can determine if they intersect with platform views on a per-picture basis. Fixes https://github.com/flutter/flutter/issues/149863 On a Macbook in Chrome in an example app with an infinite scrolling grid of platform views, this brings the ratio of dropped frames from 93% to 55% (roughly 4 fps to 30 fps). [C++, Objective-C, Java style guides]: https://github.com/flutter/engine/blob/main/CONTRIBUTING.md#style