A window should not get activated or get input focus if it's behind the lock screen.

ash/wm/ash_focus_rules_unittest.cc

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "ash/session/session_state_delegate.h"
 #include "ash/shell.h"
 #include "ash/shell_window_ids.h"
 #include "ash/test/ash_test_base.h"
 #include "ash/test/ash_test_helper.h"
 #include "ash/test/test_session_state_delegate.h"
 #include "ash/test/test_shell_delegate.h"
 #include "ash/wm/lock_state_controller.h"
 #include "ash/wm/window_state.h"
 #include "ash/wm/window_util.h"
 #include "ui/aura/client/aura_constants.h"
 #include "ui/aura/client/window_tree_client.h"
+#include "ui/views/test/widget_test.h"
 #include "ui/views/view.h"
 #include "ui/views/widget/widget.h"
 
 namespace ash {
 namespace test {
 
 namespace {
 
 // Defines a |SessionStateDelegate| that is used to create and destroy the
 // test lock screen widget.
@@ skipping 152 matching lines @@
 
   EXPECT_FALSE(shell()->session_state_delegate()->IsScreenLocked());
   EXPECT_FALSE(normal_window_state->IsMinimized());
   EXPECT_FALSE(always_on_top_window_state->IsMinimized());
   EXPECT_TRUE(normal_window_state->CanActivate());
   EXPECT_TRUE(always_on_top_window_state->CanActivate());
   EXPECT_FALSE(always_on_top_window->HasFocus());
   EXPECT_TRUE(normal_window->HasFocus());
 }
 
+// Tests that a window doesn't get activated or focused if it shows up beneath
+// the lock screen.
+TEST_F(LockScreenAshFocusRulesTest, PreventFocusChangeWithLockScreenPresent) {

[sky, 2016/03/02 03:41:02]

Please add a test close to the code you are changing.

[xdai1, 2016/03/02 21:15:55]

I think it needs to be an ash test since it requires that the lock screen blocks
the user session (so that EventClientImpl::CanProcessEventsWithinSubtree()
returns false for a window behind the lock screen). 

Could you give suggestions on where I should add the test? Thanks a lot.

[sky, 2016/03/02 22:09:09]

The code you are changing is in NativeWidgetAura. You should be able to
construct a similar configuration using aura windows. I would expect the test in
NativeWidgetAuraUnittest.

+  BlockUserSession(BLOCKED_BY_LOCK_SCREEN);
+  EXPECT_TRUE(shell()->session_state_delegate()->IsScreenLocked());
+
+  views::test::TestInitialFocusWidgetDelegate delegate(
+      shell()->GetPrimaryRootWindow());
+  EXPECT_FALSE(delegate.view()->HasFocus());
+  delegate.GetWidget()->Show();
+  EXPECT_FALSE(delegate.view()->HasFocus());
+}
+
 }  // namespace test
 }  // namespace ash