views: don't use open-folder icons in TreeView on Mac

ui/views/style/platform_style.h

 // Copyright 2015 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_VIEWS_STYLE_PLATFORM_STYLE_H_
 #define UI_VIEWS_STYLE_PLATFORM_STYLE_H_
 
 #include <memory>
 
 #include "base/macros.h"
@@ skipping 42 matching lines @@
   static const CustomButton::KeyClickAction kKeyClickActionOnSpace;
 
   // Whether the Return key clicks the focused control (on key press).
   // Otherwise, Return does nothing unless it is handled by an accelerator.
   static const bool kReturnClicksFocusedControl;
 
   // Whether selecting a row in a TreeView selects the entire row or only the
   // label for that row.
   static const bool kTreeViewSelectionPaintsEntireRow;
 
+  // Whether TreeViews use a separate icon for the currently selected node's
+  // ancestors.
+  static const bool kTreeViewUsesOpenIcon;
+
   // Whether ripples should be used for visual feedback on control activation.
   static const bool kUseRipples;
 
   // Whether to mirror the arrow of bubble dialogs in RTL, such that the bubble
   // opens in the opposite direction.
   static const bool kMirrorBubbleArrowInRTLByDefault;
 
   // Creates an ImageSkia containing the image to use for the combobox arrow.
   // The |is_enabled| argument is true if the control the arrow is for is
   // enabled, and false if the control is disabled. The |style| argument is the
@@ skipping 22 matching lines @@
   // the failed edit if platform-appropriate.
   static void OnTextfieldEditFailed();
 
  private:
   DISALLOW_IMPLICIT_CONSTRUCTORS(PlatformStyle);
 };
 
 }  // namespace views
 
 #endif  // UI_VIEWS_STYLE_PLATFORM_STYLE_H_