corrective update of Firefox 69.0.3 which solved with displaying a dialog for downloading files when you click on an email in Yahoo webmail. Additionally resolved with downloading files when launching the browser in Windows 10 with parental controls enabled.
You can also note compositing systems , written in the Rust language and outsourcing the rendering of page content to the GPU side. When using WebRender, instead of the built-in compositing system built into the Gecko engine, which processes data using the CPU, shaders running on the GPU are used to perform summary rendering operations on page elements, which allows for a significant increase in rendering speed and reduced CPU load.
WebRender added to mobile browser (Firefox replacement for Android) and enabled by default for Pixel 2 devices (other devices require gfx.webrender.all to be enabled in about:config). WebRender has also improved its image caching and rendering systems. The code for text rasterization has been reworked, which allows support for subpixel text positioning on Linux and Android platforms.
When running Firefox on top of Wayland, a new using mechanism for rendering to textures and sharing buffers with these textures located in video memory among different processes. In addition, image decoding performance optimizations have been added, using SIMD instructions for acceleration and reducing format conversion time by 5-10%.
Source: opennet.ru