[Mac][Material Design] Update Omnibox dropdown on Mac to MD

chrome/browser/ui/cocoa/omnibox/omnibox_popup_separator_view.h

 // Copyright 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.
 
 #ifndef CHROME_BROWSER_UI_COCOA_OMNIBOX_OMNIBOX_POPUP_SEPARATOR_VIEW_H_
 #define CHROME_BROWSER_UI_COCOA_OMNIBOX_OMNIBOX_POPUP_SEPARATOR_VIEW_H_
 
 #import <Cocoa/Cocoa.h>
 
 #include "chrome/browser/ui/cocoa/background_gradient_view.h"
 
 // A view used to draw a separator above omnibox popup.
 @interface OmniboxPopupTopSeparatorView : BackgroundGradientView {
 }
 
 + (CGFloat)preferredHeight;
 
 @end
 
 // A view used to draw a drop shadow beneath the omnibox popup.
 @interface OmniboxPopupBottomSeparatorView : NSView {
+ @private
+  BOOL isDarkTheme_;
 }
 
 + (CGFloat)preferredHeight;
+- (instancetype)initWithFrame:(NSRect)frame forDarkTheme:(BOOL)isDarkTheme;
 
 @end
 
 #endif  // CHROME_BROWSER_UI_COCOA_OMNIBOX_OMNIBOX_POPUP_SEPARATOR_VIEW_H_