Adds View::GetNativeTheme() to get the NativeTheme. The interesting

ui/views/widget/desktop_root_window_host_linux.cc

Index: ui/views/widget/desktop_root_window_host_linux.cc
diff --git a/ui/views/widget/desktop_root_window_host_linux.cc b/ui/views/widget/desktop_root_window_host_linux.cc
index 2304bafcaee09d1b501238cbabeb4537ed3d9991..bd500ee22af01e6726054200fd800f6c74db3665 100644
--- a/ui/views/widget/desktop_root_window_host_linux.cc
+++ b/ui/views/widget/desktop_root_window_host_linux.cc
@@ -20,6 +20,7 @@
 #include "ui/aura/shared/compound_event_filter.h"
 #include "ui/aura/shared/input_method_event_filter.h"
 #include "ui/aura/window_property.h"
+#include "ui/base/native_theme/native_theme.h"
 #include "ui/base/touch/touch_factory.h"
 #include "ui/base/x/x11_util.h"
 #include "ui/views/ime/input_method_bridge.h"
@@ -88,6 +89,11 @@ DesktopRootWindowHostLinux::DesktopRootWindowHostLinux(
 DesktopRootWindowHostLinux::~DesktopRootWindowHostLinux() {
 }
 
+// static
+ui::NativeTheme* DesktopRootWindowLinux::GetNativeTheme(aura::Window* window) {
+  return NativeTheme::instance();
+}
+
 ////////////////////////////////////////////////////////////////////////////////
 // DesktopRootWindowHostLinux, private: