linux_aura: Use GTK button borders in GTK theme mode.

chrome/browser/ui/views/toolbar/back_button.cc

 // 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.
 
 #include "chrome/browser/ui/views/toolbar/back_button.h"
 
 #include "ui/gfx/insets.h"
 #include "ui/views/controls/button/label_button_border.h"
 #include "ui/views/painter.h"
 
@@ skipping 13 matching lines @@
 }
 
 void BackButton::SetLeadingMargin(int margin) {
   // Adjust border insets to follow the margin change,
   // which will be reflected in where the border is painted
   // through |GetThemePaintRect|.
   views::LabelButtonBorder* border = new views::LabelButtonBorder(style());
   const gfx::Insets insets(border->GetInsets());
   border->set_insets(gfx::Insets(insets.top(), insets.left() + margin,
                                  insets.bottom(), insets.right()));
-  set_border(border);
+  UpdateThemedBorder(border);
 
   // Similarly fiddle the focus border. Value consistent with LabelButton
   // and TextButton.
   // TODO(gbillock): Refactor this magic number somewhere global to views,
   // probably a FocusBorder constant.
   const int kFocusRectInset = 3;
   SetFocusPainter(views::Painter::CreateDashedFocusPainterWithInsets(
                       gfx::Insets(kFocusRectInset, kFocusRectInset + margin,
                                   kFocusRectInset, kFocusRectInset)));
 
   margin_leading_ = margin;
   InvalidateLayout();
 }