Add Call answered key in TelecomManager.java

The key is used for dialer apps to know when call is answered by user.

Test: N/A
Change-Id: Idfef41b88df21a9a39032fdbb4090a181b164f73
Skip-CP-To-Master: pending on telecom review
Bug: 242074284
diff --git a/telecomm/java/android/telecom/TelecomManager.java b/telecomm/java/android/telecom/TelecomManager.java
index a72f780..1f32c97 100644
--- a/telecomm/java/android/telecom/TelecomManager.java
+++ b/telecomm/java/android/telecom/TelecomManager.java
@@ -412,6 +412,15 @@
             "android.telecom.extra.CALL_CREATED_TIME_MILLIS";
 
     /**
+     * Optional extra for incoming containing a long which specifies the time the
+     * call was answered by user. This value is in milliseconds.
+     * @hide
+     */
+    public static final String EXTRA_CALL_ANSWERED_TIME_MILLIS =
+            "android.telecom.extra.CALL_ANSWERED_TIME_MILLIS";
+
+
+    /**
      * Optional extra for incoming and outgoing calls containing a long which specifies the Epoch
      * time the call was created.
      * @hide