code style fixes

src/libcore/cell.rs

@@ -507,9 +507,11 @@ impl<T: ?Sized> Cell<T> {
     /// ```
     /// #![feature(as_cell)]
     /// use std::cell::Cell;
+    ///
     /// let slice: &mut [i32] = &mut [1, 2, 3];
     /// let cell_slice: &Cell<[i32]> = Cell::from_mut(slice);
     /// assert_eq!(cell_slice.len(), 3);
+    ///
     /// let slice_cell: &[Cell<i32>] = &cell_slice[..];
     /// assert_eq!(slice_cell.len(), 3);
     /// ```

src/test/run-pass/rfc-1789-as-cell/from-mut.rs

@@ -16,6 +16,7 @@ fn main() {
     let slice: &mut [i32] = &mut [1, 2, 3];
     let cell_slice: &Cell<[i32]> = Cell::from_mut(slice);
     assert_eq!(cell_slice.len(), 3);
+
     let sub_slice: &[Cell<i32>] = &cell_slice[1..];
     assert_eq!(sub_slice.len(), 2);
 }