patch 9.0.0825: cannot drag an entry in the tabpage line

Problem:    Cannot drag an entry in the tabpage line.
Solution:   Clear dragwin instead of got_click. (closes #11483,
            closes #11482)
diff --git a/src/testdir/test_termcodes.vim b/src/testdir/test_termcodes.vim
index cb9897e..0b2365e 100644
--- a/src/testdir/test_termcodes.vim
+++ b/src/testdir/test_termcodes.vim
@@ -562,11 +562,7 @@
       call MouseLeftClick(row, col)
       let row -= 1
       call MouseLeftDrag(row, col)
-      " FIXME: for unknown reason this test fails, related to calling
-      " reset_mouse_got_click() earlier.
-      if ttymouse_val !=# 'xterm2'
-        call assert_equal(rowseparator - 1, winheight(0) + 1, msg)
-      endif
+      call assert_equal(rowseparator - 1, winheight(0) + 1, msg)
       let row += 1
       call MouseLeftDrag(row, col)
       call assert_equal(rowseparator, winheight(0) + 1, msg)
@@ -779,6 +775,28 @@
         \              'Tab page 2',
         \              '    Xtab1'], a, msg)
 
+    " Switch to tab1
+    tabnext
+    let a = split(execute(':tabs'), "\n")
+    call assert_equal(['Tab page 1',
+        \              '    Xtab2',
+        \              'Tab page 2',
+        \              '>   Xtab1'], a, msg)
+
+    " Click in tab2 and drag it to tab1.
+    " This time it is non-current tab.
+    call MouseLeftClick(row, 6)
+    call assert_equal(0, getcharmod(), msg)
+    for col in [7, 8, 9, 10]
+      call MouseLeftDrag(row, col)
+    endfor
+    call MouseLeftRelease(row, col)
+    let a = split(execute(':tabs'), "\n")
+    call assert_equal(['Tab page 1',
+        \              '    Xtab1',
+        \              'Tab page 2',
+        \              '>   Xtab2'], a, msg)
+
     " Click elsewhere so that click in next iteration is not
     " interpreted as unwanted double-click.
     call MouseLeftClick(row, 11)