linux_aura: Use GTK button borders in GTK theme mode.

ui/views/controls/button/label_button.h

Index: ui/views/controls/button/label_button.h
diff --git a/ui/views/controls/button/label_button.h b/ui/views/controls/button/label_button.h
index f1bb3d5e178b6f71ebe5be0ece900400687f3690..1951421c2982bb11a96fdaf184d88a1350166e19 100644
--- a/ui/views/controls/button/label_button.h
+++ b/ui/views/controls/button/label_button.h
@@ -16,6 +16,7 @@
 
 namespace views {
 
+class LabelButtonBorder;
 class Painter;
 
 // LabelButton is an alternative to TextButton, it's not focusable by default.
@@ -95,6 +96,11 @@ class VIEWS_EXPORT LabelButton : public CustomButton,
   // Updates the image view to contain the appropriate button state image.
   void UpdateImage();
 
+  // Updates our border with a specific LabelButtonBorder instance which has
+  // different insets, etc. This may wrap the border in an object which will
+  // draw a native style border.
+  void UpdateThemedBorder(LabelButtonBorder* label_button_border);
+
   // NativeThemeDelegate:
   virtual gfx::Rect GetThemePaintRect() const OVERRIDE;