d91038befd
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). This is a reland of https://github.com/flutter/engine/pull/54878 with a fix for scenes with pictures that are eventually entirely clipped out. [C++, Objective-C, Java style guides]: https://github.com/flutter/engine/blob/main/CONTRIBUTING.md#style