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

ash/touch/touch_transformer_controller.cc

 // Copyright 2014 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/touch/touch_transformer_controller.h"
 
 #include "ash/display/display_manager.h"
 #include "ash/display/window_tree_host_manager.h"
 #include "ash/host/ash_window_tree_host.h"
 #include "ash/root_window_controller.h"
@@ skipping 156 matching lines @@
   DisplayManager* display_manager = GetDisplayManager();
   if (display_manager->num_connected_displays() == 0) {
     return;
   } else if (display_manager->num_connected_displays() == 1 ||
              display_manager->IsInUnifiedMode()) {
     single_display_id = display_manager->first_display_id();
     DCHECK(single_display_id != gfx::Display::kInvalidDisplayID);
     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);
     display2 = display_manager->GetDisplayInfo(display2_id);
     UpdateTouchRadius(display1);
     UpdateTouchRadius(display2);
   }
 
   gfx::Size fb_size =
       Shell::GetInstance()->display_configurator()->framebuffer_size();
@@ skipping 32 matching lines @@
 
 void TouchTransformerController::OnDisplaysInitialized() {
   UpdateTouchTransformer();
 }
 
 void TouchTransformerController::OnDisplayConfigurationChanged() {
   UpdateTouchTransformer();
 }
 
 }  // namespace ash