aura: Fix views_unittests on linux.

views/controls/scrollbar/native_scroll_bar_views.cc

 // Copyright (c) 2011 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 "views/controls/scrollbar/native_scroll_bar_views.h"
 
 #include "base/logging.h"
 #include "ui/base/keycodes/keyboard_codes.h"
 #include "ui/gfx/canvas.h"
 #include "ui/gfx/canvas_skia.h"
@@ skipping 366 matching lines @@
     bounds.set_height(thumb->GetPreferredSize().height());
   } else {
     bounds.set_y(bounds.y() + size.height());
     bounds.set_height(std::max(0, bounds.height() - 2 * size.height()));
     bounds.set_width(thumb->GetPreferredSize().width());
   }
 
   return bounds;
 }
 
+#if !defined(TOOLKIT_USES_GTK)
+////////////////////////////////////////////////////////////////////////////////
+// NativewScrollBarWrapper, public:
+
+// static
+NativeScrollBarWrapper* NativeScrollBarWrapper::CreateWrapper(
+    NativeScrollBar* scroll_bar) {
+  return new NativeScrollBarViews(scroll_bar);
+}
+
+// static
+int NativeScrollBarWrapper::GetHorizontalScrollBarHeight() {
+  return 20;
+}
+
+// static
+int NativeScrollBarWrapper::GetVerticalScrollBarWidth() {
+  return 20;
+}
+#endif
+
 }  // namespace views