use the right NativeTheme on bubbles + dialogs on Aura Linux

chrome/browser/ui/libgtk2ui/gtk2_ui.cc

Index: chrome/browser/ui/libgtk2ui/gtk2_ui.cc
diff --git a/chrome/browser/ui/libgtk2ui/gtk2_ui.cc b/chrome/browser/ui/libgtk2ui/gtk2_ui.cc
index 1feebbc86c7c69b95fa71ae125d64188257d3619..e09d73fc786e809c0cd97e7c141e8472e83be249 100644
--- a/chrome/browser/ui/libgtk2ui/gtk2_ui.cc
+++ b/chrome/browser/ui/libgtk2ui/gtk2_ui.cc
@@ -449,10 +449,21 @@ double Gtk2UI::GetCursorBlinkInterval() const {
   return cursor_blink ? (cursor_blink_time / kGtkCursorBlinkCycleFactor) : 0.0;
 }
 
-ui::NativeTheme* Gtk2UI::GetNativeTheme() const {
+ui::NativeTheme* Gtk2UI::GetNativeTheme(aura::Window* window) const {
+  ui::NativeTheme* native_theme_override = NULL;
+  if (!native_theme_overrider_.is_null())
+    native_theme_override = native_theme_overrider_.Run(window);
+
+  if (native_theme_override)
+    return native_theme_override;
+
   return NativeThemeGtk2::instance();
 }
 
+void Gtk2UI::SetNativeThemeOverride(const NativeThemeGetter& callback) {
+  native_theme_overrider_ = callback;
+}
+
 bool Gtk2UI::GetDefaultUsesSystemTheme() const {
   scoped_ptr<base::Environment> env(base::Environment::Create());