Update theme applied transition.

Bug: 126744145
Test: build and apply theme
Change-Id: I46754450265ee04b7ff2021996c8ef96f43f34ed
diff --git a/src/com/android/customization/picker/theme/ThemeFragment.java b/src/com/android/customization/picker/theme/ThemeFragment.java
index a93ff71..c1811f3 100644
--- a/src/com/android/customization/picker/theme/ThemeFragment.java
+++ b/src/com/android/customization/picker/theme/ThemeFragment.java
@@ -113,6 +113,7 @@
                     Toast.makeText(getContext(), R.string.applied_theme_msg,
                             Toast.LENGTH_LONG).show();
                     getActivity().finish();
+                    getActivity().overridePendingTransition(R.anim.fade_in, R.anim.fade_out);
                 }
 
                 @Override