API docs clarification for placing calls.

Clarifying that a dialer app should use TelecomManager to place calls
instead of relying on the Intent#ACTION_CALL intent.

Test: Docs only change.
Fixes: 202033596
Change-Id: Iac9358c5cd069f120a167c96aa6b9462313b2268
diff --git a/telecomm/java/android/telecom/InCallService.java b/telecomm/java/android/telecom/InCallService.java
index 705b491..7caaba7 100644
--- a/telecomm/java/android/telecom/InCallService.java
+++ b/telecomm/java/android/telecom/InCallService.java
@@ -69,7 +69,14 @@
  * them know that the app has crashed and that their call was continued using the pre-loaded dialer
  * app.
  * <p>
- * Further, the pre-loaded dialer will ALWAYS be used when the user places an emergency call.
+ * The pre-loaded dialer will ALWAYS be used when the user places an emergency call, even if your
+ * app fills the {@link android.app.role.RoleManager#ROLE_DIALER} role.  To ensure an optimal
+ * experience when placing an emergency call, the default dialer should ALWAYS use
+ * {@link android.telecom.TelecomManager#placeCall(Uri, Bundle)} to place calls (including
+ * emergency calls).  This ensures that the platform is able to verify that the request came from
+ * the default dialer.  If a non-preloaded dialer app uses {@link Intent#ACTION_CALL} to place an
+ * emergency call, it will be raised to the preloaded dialer app using {@link Intent#ACTION_DIAL}
+ * for confirmation; this is a suboptimal user experience.
  * <p>
  * Below is an example manifest registration for an {@code InCallService}. The meta-data
  * {@link TelecomManager#METADATA_IN_CALL_SERVICE_UI} indicates that this particular