Add telecom extra keys required for DMR release.

Bug: 22848290
Change-Id: I3328234e3f07d83d0dbe5b61b959344b6cc5cc3f
diff --git a/telecomm/java/android/telecom/TelecomManager.java b/telecomm/java/android/telecom/TelecomManager.java
index 3b59f27d..067e734 100644
--- a/telecomm/java/android/telecom/TelecomManager.java
+++ b/telecomm/java/android/telecom/TelecomManager.java
@@ -177,6 +177,13 @@
             "android.telecom.extra.PHONE_ACCOUNT_HANDLE";
 
     /**
+     * Optional extra for {@link android.content.Intent#ACTION_CALL} containing a string call
+     * subject which will be associated with an outgoing call.  Should only be specified if the
+     * {@link PhoneAccount} supports the capability {@link PhoneAccount#CAPABILITY_CALL_SUBJECT}.
+     */
+    public static final String EXTRA_CALL_SUBJECT = "android.telecom.extra.CALL_SUBJECT";
+
+    /**
      * The extra used by a {@link ConnectionService} to provide the handle of the caller that
      * has initiated a new incoming call.
      */