aura: Fix views_unittests on linux.

views/controls/scrollbar/native_scroll_bar_views.cc

Index: views/controls/scrollbar/native_scroll_bar_views.cc
diff --git a/views/controls/scrollbar/native_scroll_bar_views.cc b/views/controls/scrollbar/native_scroll_bar_views.cc
index f007b503489abaadf201b39b367851d34235b475..aaa86c1f237eb94bec82b57530200386a5cf784a 100644
--- a/views/controls/scrollbar/native_scroll_bar_views.cc
+++ b/views/controls/scrollbar/native_scroll_bar_views.cc
@@ -384,4 +384,25 @@ gfx::Rect NativeScrollBarViews::GetTrackBounds() const {
   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