Add a flag for APV support in mp4 writer

Bug: 370061501
Test: Builds

Change-Id: I5700d268967ebc53e76787cdc31539084cf66bc6
diff --git a/media/java/android/media/flags/editing.aconfig b/media/java/android/media/flags/editing.aconfig
index 185f579..0adc478 100644
--- a/media/java/android/media/flags/editing.aconfig
+++ b/media/java/android/media/flags/editing.aconfig
@@ -15,3 +15,10 @@
   description: "Enable B frames for Stagefright recorder."
   bug: "341121900"
 }
+
+flag {
+  name: "muxer_mp4_enable_apv"
+  namespace: "media_solutions"
+  description: "Enable APV support in mp4 writer."
+  bug: "370061501"
+}