Show message to indicate that mirriring with more than 3 display is not supported.

ash/display/display_util.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/display/display_util.h"
 
 #include <algorithm>
 
 #include "ash/display/display_info.h"
 #include "ash/display/display_manager.h"
 #include "ash/host/ash_window_tree_host.h"
+#include "ash/new_window_delegate.h"
 #include "ash/shell.h"
+#include "ash/system/system_notifier.h"
 #include "base/strings/string_number_conversions.h"
+#include "grit/ash_resources.h"
 #include "ui/aura/env.h"
 #include "ui/aura/window_tree_host.h"
+#include "ui/base/l10n/l10n_util.h"
+#include "ui/base/resource/resource_bundle.h"
 #include "ui/display/display.h"
 #include "ui/gfx/geometry/point.h"
 #include "ui/gfx/geometry/rect.h"
 #include "ui/gfx/geometry/size_conversions.h"
+#include "ui/message_center/message_center.h"
+#include "ui/message_center/notification.h"
+#include "ui/message_center/notification_delegate.h"
+#include "ui/message_center/notification_list.h"
 #include "ui/wm/core/coordinate_conversion.h"
 
 #if defined(OS_CHROMEOS)
 #include "base/sys_info.h"
 #endif
 
 namespace ash {
 namespace {
 
+const char kDisplayErrorNotificationId[] = "chrome://settings/display/error";
+
+// A notification delegate that will start the feedback app when the notication
+// is clicked.
+class DisplayErrorNotificationDelegate
+    : public message_center::NotificationDelegate {
+ public:
+  DisplayErrorNotificationDelegate() = default;
+
+  // message_center::NotificationDelegate:
+  bool HasClickedListener() override { return true; }
+
+  void Click() override {
+    ash::Shell::GetInstance()->new_window_delegate()->OpenFeedbackPage();
+  }
+
+ private:
+  // Private destructor since NotificationDelegate is ref-counted.
+  ~DisplayErrorNotificationDelegate() override = default;
+
+  DISALLOW_COPY_AND_ASSIGN(DisplayErrorNotificationDelegate);
+};
+
 // List of value UI Scale values. Scales for 2x are equivalent to 640,
 // 800, 1024, 1280, 1440, 1600 and 1920 pixel width respectively on
 // 2560 pixel width 2x density display. Please see crbug.com/233375
 // for the full list of resolutions.
 const float kUIScalesFor2x[] =
     {0.5f, 0.625f, 0.8f, 1.0f, 1.125f, 1.25f, 1.5f, 2.0f};
 const float kUIScalesFor1_25x[] = {0.5f, 0.625f, 0.8f, 1.0f, 1.25f };
 const float kUIScalesFor1280[] = {0.5f, 0.625f, 0.8f, 1.0f, 1.125f };
 const float kUIScalesFor1366[] = {0.5f, 0.6f, 0.75f, 1.0f, 1.125f };
 
@@ skipping 361 matching lines @@
   DCHECK_NE(id1, id2);
   // Output index is stored in the first 8 bits. See GetDisplayIdFromEDID
   // in edid_parser.cc.
   int index_1 = id1 & 0xFF;
   int index_2 = id2 & 0xFF;
   DCHECK_NE(index_1, index_2) << id1 << " and " << id2;
   return display::Display::IsInternalDisplayId(id1) ||
          (index_1 < index_2 && !display::Display::IsInternalDisplayId(id2));
 }
 
+void ShowDisplayErrorNotification(int message_id) {
+  // Always remove the notification to make sure the notification appears
+  // as a popup in any situation.
+  message_center::MessageCenter::Get()->RemoveNotification(
+      kDisplayErrorNotificationId, false /* by_user */);
+
+  ui::ResourceBundle& bundle = ui::ResourceBundle::GetSharedInstance();
+  std::unique_ptr<message_center::Notification> notification(
+      new message_center::Notification(
+          message_center::NOTIFICATION_TYPE_SIMPLE, kDisplayErrorNotificationId,
+          base::string16(),  // title
+          l10n_util::GetStringUTF16(message_id),
+          bundle.GetImageNamed(IDR_AURA_NOTIFICATION_DISPLAY),
+          base::string16(),  // display_source
+          GURL(), message_center::NotifierId(
+                      message_center::NotifierId::SYSTEM_COMPONENT,
+                      system_notifier::kNotifierDisplayError),
+          message_center::RichNotificationData(),
+          new DisplayErrorNotificationDelegate));
+  message_center::MessageCenter::Get()->AddNotification(
+      std::move(notification));
+}
+
+base::string16 GetDisplayErrorNotificationMessageForTest() {
+  message_center::NotificationList::Notifications notifications =
+      message_center::MessageCenter::Get()->GetVisibleNotifications();
+  for (message_center::NotificationList::Notifications::const_iterator iter =

[stevenjb, 2016/05/06 16:03:51]

nit: for (const auto iter : notifications)

[oshima, 2016/05/06 18:47:04]

Done.

+           notifications.begin();
+       iter != notifications.end(); ++iter) {
+    if ((*iter)->id() == kDisplayErrorNotificationId)
+      return (*iter)->message();
+  }
+  return base::string16();
+}
+
 }  // namespace ash