linux_aura: Three fixes for switching themes.

ui/linux_ui/linux_ui.h

Index: ui/linux_ui/linux_ui.h
diff --git a/ui/linux_ui/linux_ui.h b/ui/linux_ui/linux_ui.h
index 85decc8bf7348abd33920473fb213736e167cb53..1f58e111a52ae229d69f59a30e90c8dc17cbf617 100644
--- a/ui/linux_ui/linux_ui.h
+++ b/ui/linux_ui/linux_ui.h
@@ -47,10 +47,15 @@ class LINUX_UI_EXPORT LinuxUI : public LinuxShellDialog {
   virtual bool UseNativeTheme() const = 0;
   virtual gfx::Image GetThemeImageNamed(int id) const = 0;
   virtual bool GetColor(int id, SkColor* color) const = 0;
+  virtual bool HasCustomImage(int id) const = 0;
 
   // Returns a NativeTheme that will provide system colors and draw system
   // style widgets.
   virtual NativeTheme* GetNativeTheme() const = 0;
+
+  // Returns whether we should be using the native theme provided by this
+  // object by default.
+  virtual bool GetDefaultUsesSystemTheme() const = 0;
 };
 
 }  // namespace ui