Remove deprecated extension notification from themeservice.

chrome/browser/themes/theme_syncable_service_unittest.cc

Index: chrome/browser/themes/theme_syncable_service_unittest.cc
diff --git a/chrome/browser/themes/theme_syncable_service_unittest.cc b/chrome/browser/themes/theme_syncable_service_unittest.cc
index ca607be9f977157b3718f5d64e050deddb6469bf..f46c1644df3880da5b5d99e4431c3c3aa6339029 100644
--- a/chrome/browser/themes/theme_syncable_service_unittest.cc
+++ b/chrome/browser/themes/theme_syncable_service_unittest.cc
@@ -94,6 +94,9 @@ class FakeThemeService : public ThemeService {
       return std::string();
   }
 
+  // KeyedService:
+  void Shutdown() override {}
+
   const extensions::Extension* theme_extension() const {
     return theme_extension_.get();
   }