Adding extra key to indicate when the last emergency call was made.

This can be used to determine if an incoming call is potentially
an emergency callback.

Bug: 30952524
Test: none
Change-Id: I2d4ca8e6885c0314394b3a2ad389ad8115b79156
diff --git a/telecomm/java/android/telecom/Call.java b/telecomm/java/android/telecom/Call.java
index c69b7c2..b20384d 100644
--- a/telecomm/java/android/telecom/Call.java
+++ b/telecomm/java/android/telecom/Call.java
@@ -115,6 +115,13 @@
      */
     public static final String AVAILABLE_PHONE_ACCOUNTS = "selectPhoneAccountAccounts";
 
+    /**
+     * Extra key used to indicate the time (in millis) when the last outgoing emergency call was
+     * made.  This is used to identify potential emergency callbacks.
+     */
+    public static final String EXTRA_LAST_EMERGENCY_CALLBACK_TIME_MILLIS =
+            "android.telecom.extra.LAST_EMERGENCY_CALLBACK_TIME_MILLIS";
+
     public static class Details {
 
         /** Call can currently be put on hold or unheld. */