Use list instead of pair to represent the set of displays.

ash/sticky_keys/sticky_keys_overlay_unittest.cc

Index: ash/sticky_keys/sticky_keys_overlay_unittest.cc
diff --git a/ash/sticky_keys/sticky_keys_overlay_unittest.cc b/ash/sticky_keys/sticky_keys_overlay_unittest.cc
index d28c5364020cd7a99440979cb50d3a71201559a9..819bc05076c02ff7ccc6623836abd58657e9547b 100644
--- a/ash/sticky_keys/sticky_keys_overlay_unittest.cc
+++ b/ash/sticky_keys/sticky_keys_overlay_unittest.cc
@@ -46,9 +46,9 @@ TEST_F(StickyKeysOverlayTest, OverlayNotDestroyedAfterDisplayRemoved) {
   // Add a secondary display to the left of the primary one.
   UpdateDisplay("1280x1024,1980x1080");
   DisplayManager* display_manager = Shell::GetInstance()->display_manager();
-  DisplayIdPair display_ids = display_manager->GetCurrentDisplayIdPair();
-  int64_t primary_display_id = display_ids.first;
-  int64_t secondary_display_id = display_ids.second;
+  DisplayIdList display_ids = display_manager->GetCurrentDisplayIdList();
+  int64_t primary_display_id = display_ids[0];
+  int64_t secondary_display_id = display_ids[1];
   display_manager->SetLayoutForCurrentDisplays(
       DisplayLayout(DisplayLayout::LEFT, 0));