[Ash] Remove pre-MD code paths from HoverHighlightView

ash/common/system/tray/tray_constants.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 ASH_COMMON_SYSTEM_TRAY_TRAY_CONSTANTS_H_
 #define ASH_COMMON_SYSTEM_TRAY_TRAY_CONSTANTS_H_
 
 #include "ash/ash_export.h"
 
 typedef unsigned int SkColor;
@@ skipping 58 matching lines @@
 extern const int kTrayPopupDetailsIconWidth;
 extern const int kTrayPopupDetailsLabelExtraLeftMargin;
 extern const SkColor kTrayPopupHoverBackgroundColor;
 extern const int kTrayPopupScrollSeparatorHeight;
 extern const int kTrayRoundedBorderRadius;
 
 // The width of ToggleButton views including any border padding.
 extern const int kTrayToggleButtonWidth;
 
 extern const SkColor kBackgroundColor;
-extern const SkColor kHoverBackgroundColor;
 extern const SkColor kPublicAccountUserCardTextColor;
 extern const SkColor kPublicAccountUserCardNameColor;
 
 extern const SkColor kHeaderBackgroundColor;
 
 extern const SkColor kBorderDarkColor;
 extern const SkColor kBorderLightColor;
 extern const SkColor kButtonStrokeColor;
 
 extern const SkColor kHeaderTextColorNormal;
@@ skipping 58 matching lines @@
 extern const int kTrayPopupSystemInfoRowHeight;
 
 namespace test {
 const int kSettingsTrayItemViewId = 10000;
 const int kAccessibilityTrayItemViewId = 10001;
 }  // namespace test
 
 }  // namespace ash
 
 #endif  // ASH_COMMON_SYSTEM_TRAY_TRAY_CONSTANTS_H_