API: Add call service handoff trigger

Change-Id: Iee03a666e7ebc2fe326f32405174466299be9d04

api/current.txt

@@ -27601,6 +27601,7 @@ package android.telecomm {
   public final class CallServiceAdapter {
     method public void handleFailedOutgoingCall(android.telecomm.ConnectionRequest, int, java.lang.String);
     method public void handleSuccessfulOutgoingCall(java.lang.String);
+    method public void handoffCall(java.lang.String);
     method public void notifyIncomingCall(android.telecomm.CallInfo);
     method public void onPostDialWait(java.lang.String, java.lang.String);
     method public void setActive(java.lang.String);

telecomm/java/android/telecomm/CallServiceAdapter.java

@@ -224,4 +224,16 @@ public final class CallServiceAdapter {
         } catch (RemoteException ignored) {
         }
     }
+
+    /**
+     * Instructs Telecomm to handoff the call to another call service.
+     *
+     * @param callId The identifier of the call to handoff.
+     */
+    public void handoffCall(String callId) {
+        try {
+            mAdapter.handoffCall(callId);
+        } catch (RemoteException e) {
+        }
+    }
 }

telecomm/java/com/android/internal/telecomm/ICallServiceAdapter.aidl

@@ -54,4 +54,6 @@ oneway interface ICallServiceAdapter {
     void removeCall(String callId);
 
     void onPostDialWait(String callId, String remaining);
+
+    void handoffCall(String callId);
 }