Justify the message center to the right of the screen (i.e. the same place as the system menu).

ash/common/system/web_notification/web_notification_tray.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/common/system/web_notification/web_notification_tray.h"
 
 #include "ash/common/material_design/material_design_controller.h"
 #include "ash/common/session/session_state_delegate.h"
 #include "ash/common/shelf/shelf_constants.h"
 #include "ash/common/shelf/wm_shelf.h"
 #include "ash/common/shelf/wm_shelf_util.h"
+#include "ash/common/system/status_area_widget.h"
 #include "ash/common/system/tray/system_tray.h"
 #include "ash/common/system/tray/system_tray_delegate.h"
 #include "ash/common/system/tray/tray_bubble_wrapper.h"
 #include "ash/common/system/tray/tray_constants.h"
 #include "ash/common/system/tray/tray_utils.h"
 #include "ash/common/system/web_notification/ash_popup_alignment_delegate.h"
 #include "ash/common/wm_lookup.h"
 #include "ash/common/wm_root_window_controller.h"
 #include "ash/common/wm_shell.h"
 #include "ash/common/wm_window.h"
@@ skipping 67 matching lines @@
 const int kNoUnreadIconSize = 18;
 
 }  // namespace
 
 // Class to initialize and manage the WebNotificationBubble and
 // TrayBubbleWrapper instances for a bubble.
 class WebNotificationBubbleWrapper {
  public:
   // Takes ownership of |bubble| and creates |bubble_wrapper_|.
   WebNotificationBubbleWrapper(WebNotificationTray* tray,
+                               TrayBackgroundView* anchor_tray,
                                message_center::MessageBubbleBase* bubble) {
     bubble_.reset(bubble);
     views::TrayBubbleView::AnchorAlignment anchor_alignment =
         tray->GetAnchorAlignment();
     views::TrayBubbleView::InitParams init_params =
         bubble->GetInitParams(anchor_alignment);
     views::TrayBubbleView* bubble_view = views::TrayBubbleView::Create(
-        tray->GetBubbleAnchor(), tray, &init_params);
-    bubble_view->set_anchor_view_insets(tray->GetBubbleAnchorInsets());
+        anchor_tray->GetBubbleAnchor(), tray, &init_params);
+    bubble_view->set_anchor_view_insets(anchor_tray->GetBubbleAnchorInsets());
     bubble_wrapper_.reset(new TrayBubbleWrapper(tray, bubble_view));
     bubble->InitializeContents(bubble_view);
   }
 
   message_center::MessageBubbleBase* bubble() const { return bubble_.get(); }
 
   // Convenience accessors.
   views::TrayBubbleView* bubble_view() const { return bubble_->bubble_view(); }
 
  private:
@@ skipping 248 matching lines @@
     // Assume the status area and bubble bottoms are aligned when vertical.
     gfx::Rect bounds_in_root =
         status_area_window_->GetRootWindow()->ConvertRectFromScreen(
             status_area_window_->GetBoundsInScreen());
     max_height = bounds_in_root.bottom();
   }
   message_center_bubble->SetMaxHeight(
       std::max(0, max_height - GetTrayConstant(TRAY_SPACING)));
   if (show_settings)
     message_center_bubble->SetSettingsVisible();
-  message_center_bubble_.reset(
-      new WebNotificationBubbleWrapper(this, message_center_bubble));
+
+  // For vertical shelf alignments, anchor to the WebNotificationTray, but for
+  // horizontal (i.e. bottom) shelves, anchor to the system tray.
+  TrayBackgroundView* anchor_tray = this;
+  if (shelf_alignment() == SHELF_ALIGNMENT_BOTTOM) {
+    anchor_tray = WmShelf::ForWindow(status_area_window_)
+                      ->GetStatusAreaWidget()
+                      ->system_tray();
+  }
+
+  message_center_bubble_.reset(new WebNotificationBubbleWrapper(
+      this, anchor_tray, message_center_bubble));
 
   system_tray_->SetHideNotifications(true);
   shelf()->UpdateAutoHideState();
   SetIsActive(true);
   return true;
 }
 
 bool WebNotificationTray::ShowMessageCenter() {
   return ShowMessageCenterInternal(false /* show_settings */);
 }
@@ skipping 271 matching lines @@
 
 message_center::MessageCenterBubble*
 WebNotificationTray::GetMessageCenterBubbleForTest() {
   if (!message_center_bubble())
     return nullptr;
   return static_cast<message_center::MessageCenterBubble*>(
       message_center_bubble()->bubble());
 }
 
 }  // namespace ash