Add API for external call audio route.

Test: CTS test
Change-Id: Ibd1c2880e732f39281f5f6616465bf2c680c1b0d
diff --git a/telecomm/java/android/telecom/Call.java b/telecomm/java/android/telecom/Call.java
index d94fafc..ce9530c 100644
--- a/telecomm/java/android/telecom/Call.java
+++ b/telecomm/java/android/telecom/Call.java
@@ -701,8 +701,15 @@
          */
         public static final int PROPERTY_CROSS_SIM = 0x00004000;
 
+        /**
+         * Connection is a tethered external call.
+         * Indicates that the {@link Connection} is fixed on this device but the audio streams are
+         * re-routed to another device.
+         */
+        public static final int PROPERTY_TETHERED_CALL = 0x00008000;
+
         //******************************************************************************************
-        // Next PROPERTY value: 0x00004000
+        // Next PROPERTY value: 0x00010000
         //******************************************************************************************
 
         private final @CallState int mState;
@@ -899,6 +906,9 @@
             if (hasProperty(properties, PROPERTY_CROSS_SIM)) {
                 builder.append(" PROPERTY_CROSS_SIM");
             }
+            if (hasProperty(properties, PROPERTY_TETHERED_CALL)) {
+                builder.append(" PROPERTY_TETHERED_CALL");
+            }
             builder.append("]");
             return builder.toString();
         }