Update the background color of ARC notifications when notification settings is opened.

ui/message_center/message_center_style.h

 // 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.
 
 #ifndef UI_MESSAGE_CENTER_MESSAGE_CENTER_STYLE_H_
 #define UI_MESSAGE_CENTER_MESSAGE_CENTER_STYLE_H_
 
 #include <stddef.h>
 
 #include "build/build_config.h"
@@ skipping 78 matching lines @@
 const SkColor kImageBackgroundColor = kNotificationBackgroundColor;
 // Title, message, ...
 const SkColor kRegularTextColor = SkColorSetRGB(0x33, 0x33, 0x33);
 const SkColor kDimTextColor = SkColorSetRGB(0x7f, 0x7f, 0x7f);
 // The focus border.
 const SkColor kFocusBorderColor = SkColorSetRGB(64, 128, 250);
 // Foreground of small icon image.
 const SkColor kSmallImageMaskForegroundColor = SK_ColorWHITE;
 // Background of small icon image.
 const SkColor kSmallImageMaskBackgroundColor = SkColorSetRGB(0xa3, 0xa3, 0xa3);
+// Background of the close button and the settings button
+const SkColor kControlButtonBackgroundColor =
+    SkColorSetA(SK_ColorWHITE, 0.9 * 0xff);
 
 // Limits.
 
 // Given the size of an image, returns the size of the properly scaled-up image
 // which fits into |container_size|.
 MESSAGE_CENTER_EXPORT gfx::Size GetImageSizeForContainerSize(
     const gfx::Size& container_size,
     const gfx::Size& image_size);
 
 const size_t kNotificationMaximumItems = 5;     // For list notifications.
@@ skipping 53 matching lines @@
 
 const SkColor kMessageCenterBackgroundColor = SkColorSetRGB(0xee, 0xee, 0xee);
 // Separator color for the tray.
 const SkColor kFooterDelimiterColor = SkColorSetRGB(0xcc, 0xcc, 0xcc);
 // Text color for tray labels.
 const SkColor kFooterTextColor = SkColorSetRGB(0x7b, 0x7b, 0x7b);
 
 }  // namespace message_center
 
 #endif  // UI_MESSAGE_CENTER_MESSAGE_CENTER_STYLE_H_