Fix MaximizeModeController startup race

ash/wm/maximize_mode/maximize_mode_controller_unittest.cc

Index: ash/wm/maximize_mode/maximize_mode_controller_unittest.cc
diff --git a/ash/wm/maximize_mode/maximize_mode_controller_unittest.cc b/ash/wm/maximize_mode/maximize_mode_controller_unittest.cc
index 9bd694a3b25f00451dbf52ea75bdecf4f6cceb9c..759f53a0e65e699b9af42f5e6afc5587d7e8be41 100644
--- a/ash/wm/maximize_mode/maximize_mode_controller_unittest.cc
+++ b/ash/wm/maximize_mode/maximize_mode_controller_unittest.cc
@@ -16,10 +16,13 @@
 #include "ash/shell.h"
 #include "ash/test/ash_test_base.h"
 #include "base/command_line.h"
+#include "base/run_loop.h"
 #include "base/test/simple_test_tick_clock.h"
 #include "base/test/user_action_tester.h"
 #include "chromeos/accelerometer/accelerometer_reader.h"
 #include "chromeos/accelerometer/accelerometer_types.h"
+#include "chromeos/dbus/dbus_thread_manager.h"
+#include "chromeos/dbus/fake_power_manager_client.h"
 #include "ui/display/manager/display_manager.h"
 #include "ui/display/test/display_manager_test_api.h"
 #include "ui/events/event_handler.h"
@@ -583,4 +586,21 @@ TEST_F(MaximizeModeControllerTest, VerticalHingeUnstableAnglesTest) {
   }
 }
 
+// Tests that when a MaximizeModeController is created that cached tablet mode
+// state will trigger a mode update.
+TEST_F(MaximizeModeControllerTest, InitializedWhileTabletModeSwitchOn) {
+  base::RunLoop().RunUntilIdle();
+  // FakePowerManagerClient is always installed for tests
+  chromeos::FakePowerManagerClient* power_manager_client =
+      static_cast<chromeos::FakePowerManagerClient*>(
+          chromeos::DBusThreadManager::Get()->GetPowerManagerClient());
+  power_manager_client->set_tablet_mode(
+      chromeos::PowerManagerClient::TabletMode::ON);
+  MaximizeModeController controller;
+  EXPECT_FALSE(controller.IsMaximizeModeWindowManagerEnabled());
+  // PowerManagerClient callback is a posted task.
+  base::RunLoop().RunUntilIdle();
+  EXPECT_TRUE(controller.IsMaximizeModeWindowManagerEnabled());
+}
+
 }  // namespace ash