Address comments in the orignial CL

ash/display/extended_mouse_warp_controller.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/display/extended_mouse_warp_controller.h"
 
 #include <cmath>
 
 #include "ash/display/display_manager.h"
 #include "ash/display/display_util.h"
@@ skipping 86 matching lines @@
 
 ExtendedMouseWarpController::ExtendedMouseWarpController(
     aura::Window* drag_source)
     : drag_source_root_(drag_source),
       allow_non_native_event_(false) {
   ash::DisplayManager* display_manager =
       Shell::GetInstance()->display_manager();
   int64_t drag_source_id = drag_source ? GetDisplayIdFromWindow(drag_source)
                                        : gfx::Display::kInvalidDisplayID;
   DisplayList display_list = display_manager->active_display_list();
-  while (display_list.size() > 0) {
+  // Try to create a Warp region for all possible two displays combination.
+  // The following code does it by poping the last element in the list
+  // and then pairing with remaining displays in the list, until the list
+  // becomes single element.
+  while (display_list.size() > 1) {
     gfx::Display display = display_list.back();
     display_list.pop_back();
     for (const gfx::Display& peer : display_list) {
       scoped_ptr<WarpRegion> region =
           CreateWarpRegion(display, peer, drag_source_id);
       if (region)
         AddWarpRegion(std::move(region), drag_source != nullptr);
     }
   }
 }
@@ skipping 95 matching lines @@
     if (drag_source_id == a.id())
       AdjustSourceEdgeBounds(a.bounds(), snap_barrier, &a_edge);
     else if (drag_source_id == b.id())
       AdjustSourceEdgeBounds(b.bounds(), snap_barrier, &b_edge);
   }
 
   return make_scoped_ptr(new WarpRegion(a.id(), b.id(), a_edge, b_edge));
 }
 
 }  // namespace ash