window-actor: Use actual image size for capture
Previously, the clipping rectangle passed to
meta_surface_actor_get_image() was updated with the actual texture
size, but recent changes in
meta_shaped_texture_get_image() now keep
the caller's clipping rectangle unchanged.
The implementation of
meta_window_actor_capture_into() was relying on
the old behavior of updating the passed clipping rectangle, but now that
it's kept unchanged, the actual clipping rectangle used to copy the data
is wrong, which causes either a distorded image or worse, a crash of
Use the resulting cairo image size to copy the data instead of the clipping rectangle to avoid the issue and get the expected size.
Fixes: #442 (closed)