add transactional video state APIs

Bug: 311265260
Test: CTS coverage
Change-Id: I4c76e414056c90643d65e72dcb51da7d81bf36b9
diff --git a/telecomm/java/android/telecom/CallEventCallback.java b/telecomm/java/android/telecom/CallEventCallback.java
index a41c011..b0438bf 100644
--- a/telecomm/java/android/telecom/CallEventCallback.java
+++ b/telecomm/java/android/telecom/CallEventCallback.java
@@ -16,9 +16,12 @@
 
 package android.telecom;
 
+import android.annotation.FlaggedApi;
 import android.annotation.NonNull;
 import android.os.Bundle;
 
+import com.android.server.telecom.flags.Flags;
+
 import java.util.List;
 
 /**
@@ -51,6 +54,14 @@
     void onMuteStateChanged(boolean isMuted);
 
     /**
+     * Called when the video state changes.
+     *
+     * @param videoState The current video state.
+     */
+    @FlaggedApi(Flags.FLAG_TRANSACTIONAL_VIDEO_STATE)
+    default void onVideoStateChanged(@CallAttributes.CallType int videoState) {}
+
+    /**
      * Telecom is informing the client user requested call streaming but the stream can't be
      * started.
      *