Reland "Add a container view of MessageView to be used for swipe control."

This is a reland of 16ab50cc
https://chromium-review.googlesource.com/c/chromium/src/+/1184724
The original change was once reverted as it failed on
linux_chromium_chromeos_asan_rel_ng.

Original change's description:
> Add a container view of MessageView to be used for swipe control.
>
> This change adds a new container view between MessageListView and
> MessageView. The new view is intended to host buttons views for swipe
> control.
> This change also returns slided notifications when another notification
> swipe is started, so as to ensure only one swipe control can be opened.
>
> Bug: 840497
> Change-Id: Ica92933a8d3f5d92caa43a5c926252681873ede1
> Reviewed-on: https://chromium-review.googlesource.com/1184724
> Reviewed-by: Yoshiki Iguchi <yoshiki@chromium.org>
> Commit-Queue: Tatsuhisa Yamaguchi <yamaguchi@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#586198}

Bug: 840497,877983
Test: ash_unittests --gtest_filter=MessageCenterViewTest.*:MessageListViewTest.*:ArcNotificationContentViewTest.*
Change-Id: I0c53b727ab317364224894ed8e0853ae10125337
Reviewed-on: https://chromium-review.googlesource.com/1192468Reviewed-by: Stefan Kuhne <skuhne@chromium.org>
Reviewed-by: Evan Stade <estade@chromium.org>
Reviewed-by: Tetsui Ohkubo <tetsui@chromium.org>
Commit-Queue: Tatsuhisa Yamaguchi <yamaguchi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#587114}

ash/message_center/message_center_view.cc

@@ -27,6 +27,7 @@
 #include "ui/gfx/canvas.h"
 #include "ui/gfx/geometry/insets.h"
 #include "ui/gfx/geometry/rect.h"
+#include "ui/gfx/geometry/rect_conversions.h"
 #include "ui/gfx/geometry/size.h"
 #include "ui/gfx/skia_paint_util.h"
 #include "ui/message_center/message_center.h"
@@ -457,7 +458,9 @@ void MessageCenterView::OnNotificationRemoved(const std::string& id,
   // We skip repositioning during clear-all anomation, since we don't need keep
   // positions.
   if (by_user && !is_clearing_all_notifications_) {
-    message_list_view_->SetRepositionTarget(view->bounds());
+    gfx::RectF rect_f(view->x(), view->y(), view->width(), view->height());
+    views::View::ConvertRectToTarget(view, message_list_view_.get(), &rect_f);
+    message_list_view_->SetRepositionTarget(gfx::ToNearestRect(rect_f));
     // Moves the keyboard focus to the next notification if the removed
     // notification is focused so that the user can dismiss notifications
     // without re-focusing by tab key.

ash/message_center/message_center_view_unittest.cc

@@ -498,11 +498,11 @@ TEST_F(MessageCenterViewTest, DISABLED_SizeAfterUpdate) {
 TEST_F(MessageCenterViewTest, SizeAfterUpdateBelowWithRepositionTarget) {
   EXPECT_EQ(2, GetMessageListView()->child_count());
   // Make sure that notification 2 is placed above notification 1.
-  EXPECT_LT(GetNotificationView(kNotificationId2)->bounds().y(),
-            GetNotificationView(kNotificationId1)->bounds().y());
+  EXPECT_LT(GetNotificationView(kNotificationId2)->GetBoundsInScreen().y(),
+            GetNotificationView(kNotificationId1)->GetBoundsInScreen().y());
 
   GetMessageListView()->SetRepositionTarget(
-      GetNotificationView(kNotificationId1)->bounds());
+      GetNotificationView(kNotificationId1)->GetBoundsInScreen());
 
   std::unique_ptr<Notification> notification = std::make_unique<Notification>(
       NOTIFICATION_TYPE_SIMPLE, std::string(kNotificationId2),
@@ -528,11 +528,11 @@ TEST_F(MessageCenterViewTest, SizeAfterUpdateBelowWithRepositionTarget) {
 TEST_F(MessageCenterViewTest, SizeAfterUpdateOfRepositionTarget) {
   EXPECT_EQ(2, GetMessageListView()->child_count());
   // Make sure that notification 2 is placed above notification 1.
-  EXPECT_LT(GetNotificationView(kNotificationId2)->bounds().y(),
-            GetNotificationView(kNotificationId1)->bounds().y());
+  EXPECT_LT(GetNotificationView(kNotificationId2)->GetBoundsInScreen().y(),
+            GetNotificationView(kNotificationId1)->GetBoundsInScreen().y());
 
   GetMessageListView()->SetRepositionTarget(
-      GetNotificationView(kNotificationId1)->bounds());
+      GetNotificationView(kNotificationId1)->GetBoundsInScreen());
 
   std::unique_ptr<Notification> notification = std::make_unique<Notification>(
       NOTIFICATION_TYPE_SIMPLE, std::string(kNotificationId1),
@@ -571,14 +571,14 @@ TEST_F(MessageCenterViewTest, SizeAfterRemove) {
 
 TEST_F(MessageCenterViewTest, PositionAfterUpdate) {
   // Make sure that the notification 2 is placed above the notification 1.
-  EXPECT_LT(GetNotificationView(kNotificationId2)->bounds().y(),
-            GetNotificationView(kNotificationId1)->bounds().y());
+  EXPECT_LT(GetNotificationView(kNotificationId2)->GetBoundsInScreen().y(),
+            GetNotificationView(kNotificationId1)->GetBoundsInScreen().y());
 
   int previous_vertical_pos_from_bottom =
       GetMessageListView()->height() -
-      GetNotificationView(kNotificationId1)->bounds().y();
+      GetNotificationView(kNotificationId1)->GetBoundsInScreen().y();
   GetMessageListView()->SetRepositionTarget(
-      GetNotificationView(kNotificationId1)->bounds());
+      GetNotificationView(kNotificationId1)->parent()->bounds());
 
   std::unique_ptr<Notification> notification = std::make_unique<Notification>(
       NOTIFICATION_TYPE_SIMPLE, std::string(kNotificationId2),
@@ -594,21 +594,21 @@ TEST_F(MessageCenterViewTest, PositionAfterUpdate) {
   // The vertical position of the target from bottom should be kept over change.
   int current_vertical_pos_from_bottom =
       GetMessageListView()->height() -
-      GetNotificationView(kNotificationId1)->bounds().y();
+      GetNotificationView(kNotificationId1)->GetBoundsInScreen().y();
   EXPECT_EQ(previous_vertical_pos_from_bottom,
             current_vertical_pos_from_bottom);
 }
 
 TEST_F(MessageCenterViewTest, PositionAfterRemove) {
   // Make sure that the notification 2 is placed above the notification 1.
-  EXPECT_LT(GetNotificationView(kNotificationId2)->bounds().y(),
-            GetNotificationView(kNotificationId1)->bounds().y());
+  EXPECT_LT(GetNotificationView(kNotificationId2)->GetBoundsInScreen().y(),
+            GetNotificationView(kNotificationId1)->GetBoundsInScreen().y());
 
   GetMessageListView()->SetRepositionTarget(
-      GetNotificationView(kNotificationId2)->bounds());
+      GetNotificationView(kNotificationId2)->parent()->bounds());
   int previous_height = GetMessageListView()->height();
   int previous_notification2_y =
-      GetNotificationView(kNotificationId2)->bounds().y();
+      GetNotificationView(kNotificationId2)->GetBoundsInScreen().y();
 
   EXPECT_EQ(2, GetMessageListView()->child_count());
   RemoveNotification(kNotificationId2, false);
@@ -620,7 +620,7 @@ TEST_F(MessageCenterViewTest, PositionAfterRemove) {
   // Confirm that notification 1 is moved up to the place on which the
   // notification 2 was.
   EXPECT_EQ(previous_notification2_y,
-            GetNotificationView(kNotificationId1)->bounds().y());
+            GetNotificationView(kNotificationId1)->GetBoundsInScreen().y());
   // The size should be kept.
   EXPECT_EQ(previous_height, GetMessageListView()->height());
 

ash/message_center/message_list_view.cc

@@ -16,12 +16,14 @@
 #include "ui/message_center/public/cpp/message_center_constants.h"
 #include "ui/message_center/public/cpp/notification.h"
 #include "ui/message_center/views/message_view.h"
+#include "ui/message_center/views/slidable_message_view.h"
 #include "ui/views/background.h"
 #include "ui/views/border.h"
 #include "ui/views/layout/box_layout.h"
 #include "ui/views/widget/widget.h"
 
 using message_center::MessageView;
+using message_center::SlidableMessageView;
 using message_center::Notification;
 
 namespace ash {
@@ -68,7 +70,7 @@ void MessageListView::Layout() {
   }
 }
 
-void MessageListView::AddNotificationAt(MessageView* view, int index) {
+void MessageListView::AddNotificationAt(MessageView* message_view, int index) {
   // |index| refers to a position in a subset of valid children. |real_index|
   // in a list includes the invalid children, so we compute the real index by
   // walking the list until |index| number of valid children are encountered,
@@ -84,24 +86,26 @@ void MessageListView::AddNotificationAt(MessageView* view, int index) {
   }
 
   if (real_index == 0)
-    ExpandSpecifiedNotificationAndCollapseOthers(view);
+    ExpandSpecifiedNotificationAndCollapseOthers(message_view);
 
-  AddChildViewAt(view, real_index);
+  SlidableMessageView* container = new SlidableMessageView(message_view);
+  AddChildViewAt(container, real_index);
   if (GetContentsBounds().IsEmpty())
     return;
 
-  adding_views_.insert(view);
+  adding_views_.insert(container);
   DoUpdateIfPossible();
 }
 
-void MessageListView::RemoveNotification(MessageView* view) {
-  DCHECK_EQ(view->parent(), this);
+void MessageListView::RemoveNotification(MessageView* message_view) {
+  views::View* container = message_view->parent();
+  DCHECK_EQ(container->parent(), this);
 
   // TODO(yhananda): We should consider consolidating clearing_all_views_,
   // deleting_views_ and deleted_when_done_.
-  if (base::ContainsValue(clearing_all_views_, view) ||
-      deleting_views_.find(view) != deleting_views_.end() ||
-      deleted_when_done_.find(view) != deleted_when_done_.end()) {
+  if (base::ContainsValue(clearing_all_views_, container) ||
+      deleting_views_.find(container) != deleting_views_.end() ||
+      deleted_when_done_.find(container) != deleted_when_done_.end()) {
     // Let's skip deleting the view if it's already scheduled for deleting.
     // Even if we check clearing_all_views_ here, we actualy have no idea
     // whether the view is due to be removed or not because it could be in its
@@ -112,63 +116,70 @@ void MessageListView::RemoveNotification(MessageView* view) {
   }
 
   if (GetContentsBounds().IsEmpty()) {
-    delete view;
+    delete container;
   } else {
-    if (adding_views_.find(view) != adding_views_.end())
-      adding_views_.erase(view);
-    if (animator_.IsAnimating(view))
-      animator_.StopAnimatingView(view);
+    if (adding_views_.find(container) != adding_views_.end())
+      adding_views_.erase(container);
+    if (animator_.IsAnimating(container))
+      animator_.StopAnimatingView(container);
 
-    if (view->layer()) {
-      deleting_views_.insert(view);
+    if (container->layer()) {
+      deleting_views_.insert(container);
     } else {
-      delete view;
+      delete container;
     }
     DoUpdateIfPossible();
   }
 
-  int index = GetIndexOf(view);
+  int index = GetIndexOf(container);
   if (index == 0)
     ExpandTopNotificationAndCollapseOthers();
 }
 
-void MessageListView::UpdateNotification(MessageView* view,
+void MessageListView::UpdateNotification(MessageView* message_view,
                                          const Notification& notification) {
+  views::View* container = message_view->parent();
   // Skip updating the notification being cleared.
-  if (base::ContainsValue(clearing_all_views_, view))
+  if (base::ContainsValue(clearing_all_views_, container))
     return;
 
-  int index = GetIndexOf(view);
+  int index = GetIndexOf(container);
   DCHECK_LE(0, index);  // GetIndexOf is negative if not a child.
 
   if (index == 0)
-    ExpandSpecifiedNotificationAndCollapseOthers(view);
-
-  animator_.StopAnimatingView(view);
-  if (deleting_views_.find(view) != deleting_views_.end())
-    deleting_views_.erase(view);
-  if (deleted_when_done_.find(view) != deleted_when_done_.end())
-    deleted_when_done_.erase(view);
-  view->UpdateWithNotification(notification);
+    ExpandSpecifiedNotificationAndCollapseOthers(message_view);
+
+  animator_.StopAnimatingView(container);
+  if (deleting_views_.find(container) != deleting_views_.end())
+    deleting_views_.erase(container);
+  if (deleted_when_done_.find(container) != deleted_when_done_.end())
+    deleted_when_done_.erase(container);
+  message_view->UpdateWithNotification(notification);
   DoUpdateIfPossible();
 }
 
 std::pair<int, MessageView*> MessageListView::GetNotificationById(
     const std::string& id) {
   for (int i = child_count() - 1; i >= 0; --i) {
-    MessageView* view = static_cast<MessageView*>(child_at(i));
-    if (view->notification_id() == id && IsValidChild(view))
-      return std::make_pair(i, view);
+    DCHECK_EQ(std::string(SlidableMessageView::kViewClassName),
+              child_at(i)->GetClassName());
+    SlidableMessageView* container =
+        static_cast<SlidableMessageView*>(child_at(i));
+    if (container->notification_id() == id && IsValidChild(container))
+      return std::make_pair(i, container->GetMessageView());
   }
   return std::make_pair(-1, nullptr);
 }
 
 MessageView* MessageListView::GetNotificationAt(int index) {
   for (int i = child_count() - 1; i >= 0; --i) {
-    MessageView* view = static_cast<MessageView*>(child_at(i));
-    if (IsValidChild(view)) {
+    DCHECK_EQ(std::string(SlidableMessageView::kViewClassName),
+              child_at(i)->GetClassName());
+    SlidableMessageView* container =
+        static_cast<SlidableMessageView*>(child_at(i));
+    if (IsValidChild(container)) {
       if (index == 0)
-        return view;
+        return container->GetMessageView();
       index--;
     }
   }
@@ -178,8 +189,9 @@ MessageView* MessageListView::GetNotificationAt(int index) {
 size_t MessageListView::GetNotificationCount() const {
   int count = 0;
   for (int i = child_count() - 1; i >= 0; --i) {
-    const MessageView* view = static_cast<const MessageView*>(child_at(i));
-    if (IsValidChild(view))
+    const SlidableMessageView* container =
+        static_cast<const SlidableMessageView*>(child_at(i));
+    if (IsValidChild(container))
       count++;
   }
   return count;
@@ -287,8 +299,10 @@ void MessageListView::ResetRepositionSession() {
 void MessageListView::ClearAllClosableNotifications(
     const gfx::Rect& visible_scroll_rect) {
   for (int i = 0; i < child_count(); ++i) {
-    // Safe cast since all views in MessageListView are MessageViews.
-    MessageView* child = static_cast<MessageView*>(child_at(i));
+    // Safe cast since all views in MessageListView are SlidableMessageViews.
+    DCHECK_EQ(std::string(SlidableMessageView::kViewClassName),
+              child_at(i)->GetClassName());
+    SlidableMessageView* child = static_cast<SlidableMessageView*>(child_at(i));
     if (!child->visible())
       continue;
     if (gfx::IntersectRects(child->bounds(), visible_scroll_rect).IsEmpty())
@@ -480,34 +494,41 @@ void MessageListView::ExpandSpecifiedNotificationAndCollapseOthers(
   }
 
   for (int i = 0; i < child_count(); ++i) {
-    MessageView* view = static_cast<MessageView*>(child_at(i));
+    DCHECK_EQ(std::string(SlidableMessageView::kViewClassName),
+              child_at(i)->GetClassName());
+    SlidableMessageView* container =
+        static_cast<SlidableMessageView*>(child_at(i));
     // Target view is already processed above.
-    if (target_view == view)
+    if (target_view == container->GetMessageView())
       continue;
     // Skip if the view is invalid.
-    if (!IsValidChild(view))
+    if (!IsValidChild(container))
       continue;
     // We don't touch if the view has been manually expanded or collapsed.
-    if (view->IsManuallyExpandedOrCollapsed())
+    if (container->IsManuallyExpandedOrCollapsed())
       continue;
 
     // Otherwise, collapse the notification.
-    view->SetExpanded(false);
+    container->SetExpanded(false);
   }
 }
 
 void MessageListView::ExpandTopNotificationAndCollapseOthers() {
-  MessageView* top_notification = nullptr;
+  SlidableMessageView* top_notification = nullptr;
   for (int i = 0; i < child_count(); ++i) {
-    MessageView* view = static_cast<MessageView*>(child_at(i));
-    if (!IsValidChild(view))
+    DCHECK_EQ(std::string(SlidableMessageView::kViewClassName),
+              child_at(i)->GetClassName());
+    SlidableMessageView* container =
+        static_cast<SlidableMessageView*>(child_at(i));
+    if (!IsValidChild(container))
       continue;
-    top_notification = view;
+    top_notification = container;
     break;
   }
 
   if (top_notification != nullptr)
-    ExpandSpecifiedNotificationAndCollapseOthers(top_notification);
+    ExpandSpecifiedNotificationAndCollapseOthers(
+        top_notification->GetMessageView());
 }
 
 std::vector<int> MessageListView::ComputeRepositionOffsets(
@@ -669,4 +690,19 @@ void MessageListView::AnimateClearingOneNotification() {
   }
 }
 
+void MessageListView::OnSlideChanged(const std::string& notification_id) {
+  for (int i = 0; i < child_count(); ++i) {
+    DCHECK_EQ(std::string(SlidableMessageView::kViewClassName),
+              child_at(i)->GetClassName());
+    SlidableMessageView* container =
+        static_cast<SlidableMessageView*>(child_at(i));
+    MessageView* message = container->GetMessageView();
+    if (message->notification_id() == notification_id)
+      continue;
+    if (!IsValidChild(container))
+      continue;
+    container->CloseSwipeControl();
+  }
+}
+
 }  // namespace ash

ash/message_center/message_list_view.h

@@ -14,6 +14,7 @@
 #include "ui/compositor/paint_context.h"
 #include "ui/gfx/geometry/rect.h"
 #include "ui/gfx/geometry/size.h"
+#include "ui/message_center/views/slidable_message_view.h"
 #include "ui/views/animation/bounds_animator.h"
 #include "ui/views/animation/bounds_animator_observer.h"
 #include "ui/views/controls/scroll_view.h"
@@ -24,6 +25,7 @@ class Layer;
 }
 
 namespace message_center {
+class SlidableMessageView;
 class MessageView;
 class Notification;
 }  // namespace message_center
@@ -33,8 +35,10 @@ namespace ash {
 // Displays a list of messages for rich notifications. Functions as an array of
 // MessageViews and animates them on transitions. It also supports
 // repositioning.
-class ASH_EXPORT MessageListView : public views::View,
-                                   public views::BoundsAnimatorObserver {
+class ASH_EXPORT MessageListView
+    : public views::View,
+      public views::BoundsAnimatorObserver,
+      public message_center::MessageView::SlideObserver {
  public:
   class Observer {
    public:
@@ -44,9 +48,9 @@ class ASH_EXPORT MessageListView : public views::View,
   MessageListView();
   ~MessageListView() override;
 
-  void AddNotificationAt(message_center::MessageView* view, int i);
-  void RemoveNotification(message_center::MessageView* view);
-  void UpdateNotification(message_center::MessageView* view,
+  void AddNotificationAt(message_center::MessageView* message_view, int i);
+  void RemoveNotification(message_center::MessageView* message_view);
+  void UpdateNotification(message_center::MessageView* message_view,
                           const message_center::Notification& notification);
   std::pair<int, message_center::MessageView*> GetNotificationById(
       const std::string& id);
@@ -82,6 +86,9 @@ class ASH_EXPORT MessageListView : public views::View,
   }
   void set_scroller(views::ScrollView* scroller) { scroller_ = scroller; }
 
+  // Overridden from MessageView::SlideObserver
+  void OnSlideChanged(const std::string& notification_id) override;
+
  protected:
   // Overridden from views::View.
   void Layout() override;
@@ -121,7 +128,7 @@ class ASH_EXPORT MessageListView : public views::View,
 
   // Schedules animation for a child to the specified position. Returns false
   // if |child| will disappear after the animation.
-  bool AnimateChild(views::View* child,
+  bool AnimateChild(views::View* child,  // message_center::SlidableMessageView
                     int top,
                     int height,
                     bool animate_even_on_move);

ash/message_center/message_list_view_unittest.cc

@@ -17,11 +17,13 @@
 #include "ui/message_center/notification_list.h"
 #include "ui/message_center/public/cpp/notification.h"
 #include "ui/message_center/views/notification_view_md.h"
+#include "ui/message_center/views/slidable_message_view.h"
 #include "ui/views/test/views_test_base.h"
 
 using ::testing::ElementsAre;
 using message_center::Notification;
 using message_center::NotificationViewMD;
+using message_center::SlidableMessageView;
 using message_center::NotifierId;
 using message_center::NOTIFICATION_TYPE_SIMPLE;
 
@@ -435,6 +437,19 @@ TEST_F(MessageListViewTest, ClearAllClosableNotifications) {
   EXPECT_TRUE(is_on_all_notifications_cleared_called());
 }
 
+bool ContainsMessageView(MessageListView* message_list_view,
+                         NotificationViewMD* notification_view) {
+  for (int i = 0; i < message_list_view->child_count(); i++) {
+    DCHECK_EQ(std::string(SlidableMessageView::kViewClassName),
+              message_list_view->child_at(i)->GetClassName());
+    if (static_cast<SlidableMessageView*>(message_list_view->child_at(i))
+            ->GetMessageView() == notification_view) {
+      return true;
+    }
+  }
+  return false;
+}
+
 // Regression test for crbug.com/713983
 TEST_F(MessageListViewTest, RemoveWhileClearAll) {
   message_list_view()->SetBounds(0, 0, 800, 600);
@@ -460,11 +475,11 @@ TEST_F(MessageListViewTest, RemoveWhileClearAll) {
   RunPendingAnimations();
 
   // Call RemoveNotification()
-  EXPECT_TRUE(message_list_view()->Contains(notification_view2));
+  EXPECT_TRUE(ContainsMessageView(message_list_view(), notification_view2));
   message_list_view()->RemoveNotification(notification_view2);
 
   // Call "Clear All" while notification_view2 is still in message_list_view.
-  EXPECT_TRUE(message_list_view()->Contains(notification_view2));
+  EXPECT_TRUE(ContainsMessageView(message_list_view(), notification_view2));
   message_list_view()->ClearAllClosableNotifications(
       message_list_view()->bounds());
 

ash/system/unified/unified_message_center_view.cc

@@ -345,6 +345,7 @@ void UnifiedMessageCenterView::AddNotificationAt(
   MessageView* view = message_center::MessageViewFactory::Create(
       notification, /*top-level=*/false);
   view->AddObserver(this);
+  view->AddSlideObserver(message_list_view_);
   view->set_scroller(scroller_);
   message_list_view_->AddNotificationAt(view, index);
 }

ui/message_center/BUILD.gn

@@ -144,6 +144,8 @@ jumbo_component("message_center") {
         "views/popup_alignment_delegate.h",
         "views/proportional_image_view.cc",
         "views/proportional_image_view.h",
+        "views/slidable_message_view.cc",
+        "views/slidable_message_view.h",
         "views/slide_out_controller.cc",
         "views/slide_out_controller.h",
       ]

ui/message_center/views/message_view.cc

@@ -310,7 +310,15 @@ ui::Layer* MessageView::GetSlideOutLayer() {
   return is_nested_ ? layer() : GetWidget()->GetLayer();
 }
 
-void MessageView::OnSlideChanged() {}
+void MessageView::OnSlideChanged() {
+  for (auto* observer : slide_observers_) {
+    observer->OnSlideChanged(notification_id_);
+  }
+}
+
+void MessageView::AddSlideObserver(MessageView::SlideObserver* observer) {
+  slide_observers_.push_back(observer);
+}
 
 void MessageView::OnSlideOut() {
   MessageCenter::Get()->RemoveNotification(notification_id_,
@@ -358,10 +366,12 @@ void MessageView::OnCloseButtonPressed() {
 }
 
 void MessageView::OnSettingsButtonPressed(const ui::Event& event) {
+  slide_out_controller_.CloseSwipeControl();
   MessageCenter::Get()->ClickOnSettingsButton(notification_id_);
 }
 
 void MessageView::OnSnoozeButtonPressed(const ui::Event& event) {
+  slide_out_controller_.CloseSwipeControl();
   // No default implementation for snooze.
 }
 

ui/message_center/views/message_view.h

@@ -42,6 +42,11 @@ class MESSAGE_CENTER_EXPORT MessageView : public views::InkDropHostView,
  public:
   static const char kViewClassName[];
 
+  class SlideObserver {
+   public:
+    virtual void OnSlideChanged(const std::string& notification_id) = 0;
+  };
+
   enum class Mode {
     // Normal mode.
     NORMAL = 0,
@@ -117,6 +122,8 @@ class MESSAGE_CENTER_EXPORT MessageView : public views::InkDropHostView,
   void OnSlideChanged() override;
   void OnSlideOut() override;
 
+  void AddSlideObserver(SlideObserver* observer);
+
   Mode GetMode() const;
 
   // Gets the current horizontal scroll offset of the view by slide gesture.
@@ -166,6 +173,7 @@ class MESSAGE_CENTER_EXPORT MessageView : public views::InkDropHostView,
   std::unique_ptr<views::Painter> focus_painter_;
 
   SlideOutController slide_out_controller_;
+  std::vector<SlideObserver*> slide_observers_;
 
   // True if |this| is embedded in another view. Equivalent to |!top_level| in
   // MessageViewFactory parlance.

ui/message_center/views/notification_view_md_unittest.cc

@@ -92,8 +92,10 @@ class NotificationTestDelegate : public NotificationDelegate {
   DISALLOW_COPY_AND_ASSIGN(NotificationTestDelegate);
 };
 
-class NotificationViewMDTest : public views::ViewsTestBase,
-                               public views::ViewObserver {
+class NotificationViewMDTest
+    : public views::ViewsTestBase,
+      public views::ViewObserver,
+      public message_center::MessageView::SlideObserver {
  public:
   NotificationViewMDTest();
   ~NotificationViewMDTest() override;
@@ -113,6 +115,9 @@ class NotificationViewMDTest : public views::ViewsTestBase,
     return widget_;
   }
 
+  // Overridden from message_center::MessageView::Observer:
+  void OnSlideChanged(const std::string& notification_id) override {}
+
  protected:
   const gfx::Image CreateTestImage(int width, int height) const;
   const SkBitmap CreateBitmap(int width, int height) const;

ui/message_center/views/slidable_message_view.cc

+// Copyright (c) 2018 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 "ui/message_center/views/slidable_message_view.h"
+
+#include "ui/message_center/public/cpp/features.h"
+#include "ui/message_center/public/cpp/message_center_constants.h"
+#include "ui/message_center/views/message_view.h"
+#include "ui/views/background.h"
+#include "ui/views/layout/fill_layout.h"
+#include "ui/views/view.h"
+
+namespace message_center {
+
+SlidableMessageView::SlidableMessageView(MessageView* message_view)
+    : message_view_(message_view) {
+  SetFocusBehavior(views::View::FocusBehavior::NEVER);
+
+  // Draw on its own layer to allow bound animation.
+  SetPaintToLayer();
+  layer()->SetFillsBoundsOpaquely(false);
+  if (base::FeatureList::IsEnabled(message_center::kNotificationSwipeControl))
+    SetBackground(views::CreateSolidBackground(kSwipeControlBackgroundColor));
+
+  SetLayoutManager(std::make_unique<views::FillLayout>());
+
+  // TODO(crbug.com/840497): Add button container child view.
+
+  message_view_->AddSlideObserver(this);
+  AddChildView(message_view);
+}
+
+SlidableMessageView::~SlidableMessageView() = default;
+
+void SlidableMessageView::OnSlideChanged(const std::string& notification_id) {
+  // TODO(crbug.com/840497): Show/hide control buttons.
+}
+
+void SlidableMessageView::CloseSwipeControl() {
+  message_view_->CloseSwipeControl();
+}
+
+void SlidableMessageView::ChildPreferredSizeChanged(views::View* child) {
+  PreferredSizeChanged();
+  InvalidateLayout();
+}
+
+void SlidableMessageView::ChildVisibilityChanged(views::View* child) {
+  PreferredSizeChanged();
+  InvalidateLayout();
+}
+
+void SlidableMessageView::UpdateWithNotification(
+    const Notification& notification) {
+  message_view_->UpdateWithNotification(notification);
+}
+
+gfx::Size SlidableMessageView::CalculatePreferredSize() const {
+  return message_view_->GetPreferredSize();
+}
+
+int SlidableMessageView::GetHeightForWidth(int width) const {
+  return message_view_->GetHeightForWidth(width);
+}
+
+}  // namespace message_center

ui/message_center/views/slidable_message_view.h

+// Copyright (c) 2018 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.
+
+#ifndef UI_MESSAGE_CENTER_VIEWS_SLIDABLE_MESSAGE_VIEW_H_
+#define UI_MESSAGE_CENTER_VIEWS_SLIDABLE_MESSAGE_VIEW_H_
+
+#include "ui/message_center/views/message_view.h"
+#include "ui/views/view.h"
+
+namespace message_center {
+
+class MESSAGE_CENTER_EXPORT SlidableMessageView
+    : public views::View,
+      public MessageView::SlideObserver {
+ public:
+  SlidableMessageView(message_center::MessageView* message_view);
+  ~SlidableMessageView() override;
+
+  MessageView* GetMessageView() const { return message_view_; }
+
+  // MessageView::SlideObserver
+  void OnSlideChanged(const std::string& notification_id) override;
+
+  NotificationControlButtonsView* GetControlButtonsView() {
+    return message_view_->GetControlButtonsView();
+  }
+
+  void UpdateControlButtonsVisibility() {
+    return message_view_->UpdateControlButtonsVisibility();
+  }
+
+  void SetExpanded(bool expanded) {
+    return message_view_->SetExpanded(expanded);
+  }
+
+  bool IsExpanded() const { return message_view_->IsExpanded(); }
+
+  bool IsAutoExpandingAllowed() const {
+    return message_view_->IsAutoExpandingAllowed();
+  }
+
+  bool IsCloseButtonFocused() const {
+    return message_view_->IsCloseButtonFocused();
+  }
+
+  bool IsManuallyExpandedOrCollapsed() const {
+    return message_view_->IsManuallyExpandedOrCollapsed();
+  }
+
+  void SetManuallyExpandedOrCollapsed(bool value) {
+    return message_view_->SetManuallyExpandedOrCollapsed(value);
+  }
+
+  // Updates this view with the new data contained in the notification.
+  void UpdateWithNotification(const Notification& notification);
+
+  std::string notification_id() const {
+    return message_view_->notification_id();
+  }
+
+  MessageView::Mode GetMode() const { return message_view_->GetMode(); }
+
+  void CloseSwipeControl();
+
+  void StartDismissAnimation();
+
+  // views::View
+  void ChildPreferredSizeChanged(views::View* child) override;
+  void ChildVisibilityChanged(views::View* child) override;
+  gfx::Size CalculatePreferredSize() const override;
+  int GetHeightForWidth(int width) const override;
+
+ private:
+  MessageView* message_view_;
+  // TODO(crbug.com/840497): Add child view containing settings and snooze
+  // buttons.
+};
+
+}  // namespace message_center
+
+#endif  // UI_MESSAGE_CENTER_VIEWS_SLIDABLE_MESSAGE_VIEW_H_q
\ No newline at end of file