wgpu-hal creates every swapchain with `preTransform = IDENTITY` (#3345).
On a tablet whose panel is mounted landscape, a portrait window then
hands Android an unrotated buffer: SurfaceFlinger falls back to rotating
it on the GPU (composition CLIENT), and on this device those frames tear.
That is why Android draws with Skia over OpenGL today, and why the
develop view pays a readback (TD-1).
The field cannot just be set to `currentTransform` inside wgpu. It is a
promise that the image is already drawn rotated and sized in the panel's
orientation, and only the renderer above wgpu can keep it. So the patch
is the smallest thing that lets that renderer ask:
`vulkan::Surface::current_transform` reads the surface's transform, and
`set_pre_transform` makes the next swapchain use it. The default stays
IDENTITY, so desktop and any caller that does not opt in behave exactly
as upstream.
dtourolle
dc9da52651