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

ash/shelf/shelf_layout_manager.cc

 // Copyright (c) 2012 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/shelf/shelf_layout_manager.h"
 
 #include <algorithm>
 #include <cmath>
 #include <cstring>
 #include <string>
@@ skipping 687 matching lines @@
     // animate. Override the animation settings to immediately set the
     // visibility property. Opacity will still animate.
 
     // TODO(harrym): Once status area widget is a child view of shelf
     // this can be simplified.
     gfx::Rect status_bounds = target_bounds.status_bounds_in_shelf;
     status_bounds.set_x(status_bounds.x() +
                         target_bounds.shelf_bounds_in_root.x());
     status_bounds.set_y(status_bounds.y() +
                         target_bounds.shelf_bounds_in_root.y());
+    LOG(ERROR) << "Status Area Widget Bounds:"

[msw, 2016/02/02 22:54:10]

Did you mean to land this? It's spamming logs, like this:
https://build.chromium.org/p/chromium.memory.fyi/builders/Linux%20ChromeOS%20...

+               << ScreenUtil::ConvertRectToScreen(
+                      shelf_->status_area_widget()->GetNativeView()->parent(),
+                      status_bounds)
+                      .ToString();
+
     shelf_->status_area_widget()->SetBounds(
         ScreenUtil::ConvertRectToScreen(
             shelf_->status_area_widget()->GetNativeView()->parent(),
             status_bounds));
     if (!state_.is_screen_locked) {
       gfx::Insets insets;
       // If user session is blocked (login to new user session or add user to
       // the existing session - multi-profile) then give 100% of work area only
       // if keyboard is not shown.
       if (!state_.is_adding_user_screen || !keyboard_bounds_.IsEmpty()) {
@@ skipping 487 matching lines @@
     return false;
   }
   if (session_state_delegate->IsUserSessionBlocked() ||
       state_.is_adding_user_screen) {
     return true;
   }
   return false;
 }
 
 }  // namespace ash