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

ash/touch/touch_transformer_controller.cc

Index: ash/touch/touch_transformer_controller.cc
diff --git a/ash/touch/touch_transformer_controller.cc b/ash/touch/touch_transformer_controller.cc
index 0af8c8d86e4f6aa5a307ca04f170f9bb45d64f24..8bea2bf5ea794911bfb26b7d28cab15716c56429 100644
--- a/ash/touch/touch_transformer_controller.cc
+++ b/ash/touch/touch_transformer_controller.cc
@@ -174,9 +174,9 @@ void TouchTransformerController::UpdateTouchTransformer() const {
     single_display = display_manager->GetDisplayInfo(single_display_id);
     UpdateTouchRadius(single_display);
   } else {
-    DisplayIdPair id_pair = display_manager->GetCurrentDisplayIdPair();
-    display1_id = id_pair.first;
-    display2_id = id_pair.second;
+    DisplayIdList list = display_manager->GetCurrentDisplayIdList();
+    display1_id = list[0];
+    display2_id = list[1];
     DCHECK(display1_id != gfx::Display::kInvalidDisplayID &&
            display2_id != gfx::Display::kInvalidDisplayID);
     display1 = display_manager->GetDisplayInfo(display1_id);