Revert "cros: Add a double separator above context menu notifications"

This reverts commit 1c822163.

Reason for revert: 

Linker failures:
obj/ash/app_menu/app_menu/notification_menu_view.o:notification_menu_view.cc:function ash::NotificationMenuView::NotificationMenuView(ash::NotificationItemView::Delegate*, message_center::SlideOutController::Delegate*, std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&): error: undefined reference to 'vtable for views::MenuSeparator'
../../third_party/binutils/Linux_x64/Release/bin/ld.gold: the vtable symbol may be undefined because the class is missing its key function

Bug: 861885

Original change's description:
> cros: Add a double separator above context menu notifications
> 
> Add and remove a double separator with NOTIFICATION_CONTAINER.
> 
> Bug: 843761
> Change-Id: I45fb095079aaaf108a9a18958ab4e431072e588d
> Reviewed-on: https://chromium-review.googlesource.com/1121243
> Commit-Queue: Alex Newcomer <newcomer@chromium.org>
> Reviewed-by: Michael Wasserman <msw@chromium.org>
> Reviewed-by: James Cook <jamescook@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#573418}

TBR=jamescook@chromium.org,msw@chromium.org,newcomer@chromium.org

Change-Id: I10ce18a75e80116fa8d7a530d18e979a2dfbb395
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: 843761
Reviewed-on: https://chromium-review.googlesource.com/1129661Reviewed-by: Alex Newcomer <newcomer@chromium.org>
Commit-Queue: Alex Newcomer <newcomer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#573429}

ash/app_menu/notification_menu_view.cc

@@ -7,12 +7,10 @@
 #include "ash/app_menu/notification_item_view.h"
 #include "ash/app_menu/notification_menu_header_view.h"
 #include "ash/public/cpp/app_menu_constants.h"
-#include "ui/base/models/menu_separator_types.h"
 #include "ui/gfx/geometry/size.h"
 #include "ui/message_center/public/cpp/notification.h"
 #include "ui/message_center/views/proportional_image_view.h"
 #include "ui/views/controls/menu/menu_item_view.h"
-#include "ui/views/controls/menu/menu_separator.h"
 #include "ui/views/layout/box_layout.h"
 
 namespace ash {
@@ -33,10 +31,6 @@ NotificationMenuView::NotificationMenuView(
   SetLayoutManager(std::make_unique<views::BoxLayout>(
       views::BoxLayout::Orientation::kVertical));
 
-  double_separator_ =
-      new views::MenuSeparator(ui::MenuSeparatorType::DOUBLE_SEPARATOR);
-  AddChildView(double_separator_);
-
   header_view_ = new NotificationMenuHeaderView();
   AddChildView(header_view_);
 }
@@ -48,10 +42,9 @@ bool NotificationMenuView::IsEmpty() const {
 }
 
 gfx::Size NotificationMenuView::CalculatePreferredSize() const {
-  return gfx::Size(views::MenuConfig::instance().touchable_menu_width,
-                   double_separator_->GetPreferredSize().height() +
-                       header_view_->GetPreferredSize().height() +
-                       kNotificationItemViewHeight);
+  return gfx::Size(
+      views::MenuConfig::instance().touchable_menu_width,
+      header_view_->GetPreferredSize().height() + kNotificationItemViewHeight);
 }
 
 void NotificationMenuView::AddNotificationItemView(

ash/app_menu/notification_menu_view.h

@@ -17,10 +17,6 @@ namespace message_center {
 class Notification;
 }
 
-namespace views {
-class MenuSeparator;
-}
-
 namespace ash {
 
 class NotificationMenuHeaderView;
@@ -75,13 +71,9 @@ class APP_MENU_EXPORT NotificationMenuView : public views::View {
   // which is shown.
   std::deque<std::unique_ptr<NotificationItemView>> notification_item_views_;
 
-  // Holds the header and counter texts. Owned by views hierarchy.
+  // Holds the header and counter texts. Owned by this.
   NotificationMenuHeaderView* header_view_ = nullptr;
 
-  // A double separator used to distinguish notifications from context menu
-  // options. Owned by views hierarchy.
-  views::MenuSeparator* double_separator_;
-
   DISALLOW_COPY_AND_ASSIGN(NotificationMenuView);
 };