I'm not sure what part confused you: I meant literally just storing the size you're going to resize the render to somewhere, such as a resize_to: Option<Size> of some sort.
In wgpu terms, I believe the minimum is that after a resize you must call Surface::configure with the size you just got from the resize event after you have finished presenting the last frame and released the SurfaceTexture using the old size, and before you get the next SurfaceTexture with Surface::get_current_texture, though you'll also need to update the depth buffer, viewport, projection matrix and maybe things like post effect buffers that match the surface size for things to look right.