ScrollWindow should call ScrollWindowEx with the SW_ERASE flag

dlls/user/tests/msg.c

@@ -5471,6 +5471,14 @@ static void test_scrollwindowex(void)
     while (PeekMessage( &msg, 0, 0, 0, PM_REMOVE )) DispatchMessage( &msg );
     ok_sequence(ScrollWindowPaint1, "ScrollWindowEx", 0);
 
+    /* now scroll with ScrollWindow() */
+    trace("start scroll with ScrollWindow\n");
+    ScrollWindow( hwnd, 5, 5, NULL, NULL);
+    trace("end scroll\n");
+    flush_sequence();
+    while (PeekMessage( &msg, 0, 0, 0, PM_REMOVE )) DispatchMessage( &msg );
+    ok_sequence(ScrollWindowPaint1, "ScrollWindow", 0);
+
     ok(DestroyWindow(hchild), "failed to destroy window\n");
     ok(DestroyWindow(hwnd), "failed to destroy window\n");
     flush_sequence();

windows/scroll.c

@@ -182,7 +182,7 @@ BOOL WINAPI ScrollWindow( HWND hwnd, INT dx, INT dy,
     return
         (ERROR != ScrollWindowEx( hwnd, dx, dy, rect, clipRect, 0, NULL,
                                     (rect ? 0 : SW_SCROLLCHILDREN) |
-                                    SW_INVALIDATE ));
+                                    SW_INVALIDATE | SW_ERASE ));
 }
 
 /*************************************************************************