Add an empty message to the notification center.

ui/message_center/cocoa/tray_view_controller_unittest.mm

 // Copyright (c) 2013 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.
 
 #import "ui/message_center/cocoa/tray_view_controller.h"
 
 #include "base/mac/scoped_nsobject.h"
 #include "base/message_loop/message_loop.h"
 #include "base/run_loop.h"
 #include "base/strings/utf_string_conversions.h"
@@ skipping 80 matching lines @@
   EXPECT_CGFLOAT_EQ(2 * message_center::kMarginBetweenItems,
                     NSHeight([view frame]) - NSHeight(notification_frame));
   EXPECT_CGFLOAT_EQ(2 * message_center::kMarginBetweenItems,
                     NSWidth([view frame]) - NSWidth(notification_frame));
   EXPECT_GT(NSHeight([[tray_ view] frame]),
             NSHeight([[tray_ scrollView] frame]));
 
   center_->RemoveNotification("1", true);
   [tray_ onMessageCenterTrayChanged];
   EXPECT_EQ(0u, [[view subviews] count]);
-  EXPECT_CGFLOAT_EQ(0, NSHeight([view frame]));
+  // The empty tray is now 100px tall to accommodate
+  // the empty message.
+  EXPECT_CGFLOAT_EQ(message_center::kMinScrollViewHeight,
+                    NSHeight([view frame]));
 }
 
 TEST_F(TrayViewControllerTest, AddThreeClearAll) {
   NSScrollView* view = [[tray_ scrollView] documentView];
   EXPECT_EQ(0u, [[view subviews] count]);
   scoped_ptr<message_center::Notification> notification;
   notification.reset(new message_center::Notification(
       message_center::NOTIFICATION_TYPE_SIMPLE,
       "1",
       ASCIIToUTF16("First notification"),
@@ skipping 27 matching lines @@
       NULL));
   center_->AddNotification(notification.Pass());
   [tray_ onMessageCenterTrayChanged];
   ASSERT_EQ(3u, [[view subviews] count]);
 
   [tray_ clearAllNotifications:nil];
   WaitForAnimationEnded();
   [tray_ onMessageCenterTrayChanged];
 
   EXPECT_EQ(0u, [[view subviews] count]);
-  EXPECT_CGFLOAT_EQ(0, NSHeight([view frame]));
+  // The empty tray is now 100px tall to accommodate
+  // the empty message.
+  EXPECT_CGFLOAT_EQ(message_center::kMinScrollViewHeight,
+                    NSHeight([view frame]));
 }
 
 TEST_F(TrayViewControllerTest, NoClearAllWhenNoNotifications) {
   EXPECT_TRUE([tray_ pauseButton]);
   EXPECT_TRUE([tray_ clearAllButton]);
 
   // With no notifications, the clear all button should be hidden.
   EXPECT_TRUE([[tray_ clearAllButton] isHidden]);
   EXPECT_LT(NSMinX([[tray_ clearAllButton] frame]),
             NSMinX([[tray_ pauseButton] frame]));
@@ skipping 77 matching lines @@
   EXPECT_LT(trayHeight, NSHeight([[tray_ view] frame]));
 
   [tray_ showMessages:nil];
   EXPECT_EQ(1, provider.closed_called_count());
   EXPECT_TRUE(center_->IsMessageCenterVisible());
 
   // The tray should be back at its previous height now.
   EXPECT_EQ(trayHeight, NSHeight([[tray_ view] frame]));
 }
 
+TEST_F(TrayViewControllerTest, EmptyCenter) {
+  EXPECT_FALSE([[tray_ emptyDescription] isHidden]);
+
+  // With no notifications, the divider should be hidden.
+  EXPECT_TRUE([[tray_ divider] isHidden]);
+  EXPECT_TRUE([[tray_ scrollView] isHidden]);
+
+  scoped_ptr<message_center::Notification> notification;
+  notification.reset(new message_center::Notification(
+      message_center::NOTIFICATION_TYPE_SIMPLE,
+      "1",
+      ASCIIToUTF16("First notification"),
+      ASCIIToUTF16("This is a simple test."),
+      gfx::Image(),
+      base::string16(),
+      DummyNotifierId(),
+      message_center::RichNotificationData(),
+      NULL));
+  center_->AddNotification(notification.Pass());
+  [tray_ onMessageCenterTrayChanged];
+
+  EXPECT_FALSE([[tray_ divider] isHidden]);
+  EXPECT_FALSE([[tray_ scrollView] isHidden]);
+  EXPECT_TRUE([[tray_ emptyDescription] isHidden]);
+}
+
 }  // namespace message_center