vim-patch:8.1.1347: fractional scroll position not restored after closing window

Problem:    Fractional scroll position not restored after closing window.
Solution:   Do restore fraction if topline is not one.
bd2d68c2f4

src/nvim/testdir/test_window_cmd.vim

@@ -758,15 +758,7 @@ endfunc
 
 func Test_split_noscroll()
   let so_save = &so
-  new
-  only
-
-  " Make sure windows can hold all content after split.
-  for i in range(1, 20)
-    wincmd +
-    redraw!
-  endfor
-
+  enew
   call setline(1, range(1, 8))
   normal 100%
   split
@@ -782,12 +774,20 @@ func Test_split_noscroll()
   call assert_equal(1, info1.topline)
   call assert_equal(1, info2.topline)
 
-  " Restore original state.
-  for i in range(1, 20)
-    wincmd -
-    redraw!
-  endfor
+  " window that fits all lines by itself, but not when split: closing other
+  " window should restore fraction.
   only!
+  call setline(1, range(1, &lines - 10))
+  exe &lines / 4
+  let winid1 = win_getid()
+  let info1 = getwininfo(winid1)[0]
+  call assert_equal(1, info1.topline)
+  new
+  redraw
+  close
+  let info1 = getwininfo(winid1)[0]
+  call assert_equal(1, info1.topline)
+
   bwipe!
   let &so = so_save
 endfunc

src/nvim/window.c

@@ -5613,10 +5613,11 @@ void scroll_to_fraction(win_T *wp, int prev_height)
   // Don't change w_topline in any of these cases:
   // - window height is 0
   // - 'scrollbind' is set and this isn't the current window
-  // - window height is sufficient to display the whole buffer
+  // - window height is sufficient to display the whole buffer and first line
+  //   is visible.
   if (height > 0
       && (!wp->w_p_scb || wp == curwin)
-      && (height < wp->w_buffer->b_ml.ml_line_count)
+      && (height < wp->w_buffer->b_ml.ml_line_count || wp->w_topline > 1)
       ) {
     /*
      * Find a value for w_topline that shows the cursor at the same