patch 9.0.0780: 'scroll' value computed in unexpected location

Problem:    'scroll' value computed in unexpected location.
Solution:   Compute 'scroll' when the window height is changed. (Luuk van
            Baal, closes #11387)
diff --git a/src/version.c b/src/version.c
index b872e3f..947f653 100644
--- a/src/version.c
+++ b/src/version.c
@@ -696,6 +696,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    780,
+/**/
     779,
 /**/
     778,
diff --git a/src/window.c b/src/window.c
index 51416af..8d61def 100644
--- a/src/window.c
+++ b/src/window.c
@@ -6378,7 +6378,6 @@
 	    invalidate_botline_win(wp);
 	    validate_botline_win(wp);
 	}
-	win_comp_scroll(wp);
 	wp->w_prev_height = wp->w_height;
 	wp->w_prev_winrow = wp->w_winrow;
     }
@@ -6472,6 +6471,7 @@
 
     wp->w_height = height;
     wp->w_skipcol = 0;
+    win_comp_scroll(wp);
 
     // There is no point in adjusting the scroll position when exiting.  Some
     // values might be invalid.
@@ -6596,7 +6596,6 @@
     if (prev_height > 0)
 	wp->w_prev_fraction_row = wp->w_wrow;
 
-    win_comp_scroll(wp);
     redraw_win_later(wp, UPD_SOME_VALID);
     wp->w_redr_status = TRUE;
     invalidate_botline_win(wp);