error: use of deprecated item 'std::mem::uninitialized': use `mem::MaybeUninit` instead
   --> gfx/wr/webrender/src/prim_store/gradient.rs:665:77
    |
665 |         let mut entries: [GradientDataEntry; GRADIENT_DATA_SIZE] = unsafe { mem::uninitialized() };
    |                                                                             ^^^^^^^^^^^^^^^^^^
    |
    = note: `-D deprecated` implied by `-D warnings`
error: use of deprecated item 'std::mem::uninitialized': use `mem::MaybeUninit` instead
    --> gfx/wr/webrender/src/renderer.rs:1602:32
     |
1602 |             data.push(unsafe { mem::uninitialized() });
     |                                ^^^^^^^^^^^^^^^^^^
error: use of deprecated item 'std::mem::uninitialized': use `mem::MaybeUninit` instead
    --> gfx/wr/webrender/src/renderer.rs:1610:36
     |
1610 |                 data.push(unsafe { mem::uninitialized() });
     |                                    ^^^^^^^^^^^^^^^^^^
error: use of deprecated item 'std::mem::uninitialized': use `mem::MaybeUninit` instead
   --> gfx/wr/webrender/src/platform/unix/font.rs:538:42
    |
538 |         let mut cbox: FT_BBox = unsafe { mem::uninitialized() };
    |                                          ^^^^^^^^^^^^^^^^^^
error: use of deprecated item 'std::mem::uninitialized': use `mem::MaybeUninit` instead
   --> gfx/wr/webrender/src/platform/unix/font.rs:721:37
    |
721 |             let mut cbox: FT_BBox = mem::uninitialized();
    |                                     ^^^^^^^^^^^^^^^^^^

Just like in https://bugzilla.mozilla.org/show_bug.cgi?id=1595212