Give Ash material design tray items the correct size and layout

ash/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/system/web_notification/web_notification_tray.h"
 
 #include "ash/common/ash_switches.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"
@@ skipping 143 matching lines @@
   void SetUnreadCount(int unread_count) {
     // base::FormatNumber doesn't convert to arabic numeric characters.
     // TODO(mukai): use ICU to support conversion for such locales.
     unread_count_ = unread_count;
     UpdateIconVisibility();
   }
 
  protected:
   // Overridden from views::ImageButton:
   gfx::Size GetPreferredSize() const override {
-    return gfx::Size(kShelfItemHeight, kShelfItemHeight);
+    const int size = GetTrayConstant(TRAY_ITEM_HEIGHT_LEGACY);
+    return gfx::Size(size, size);
   }
 
   int GetHeightForWidth(int width) const override {
     return GetPreferredSize().height();
   }
 
  private:
   void UpdateIconVisibility() {
     if (unread_count_ == 0) {
       if (!Contains(&no_unread_icon_)) {
@@ skipping 358 matching lines @@
 
 message_center::MessageCenterBubble*
 WebNotificationTray::GetMessageCenterBubbleForTest() {
   if (!message_center_bubble())
     return NULL;
   return static_cast<message_center::MessageCenterBubble*>(
       message_center_bubble()->bubble());
 }
 
 }  // namespace ash