API tweaks in response to feedback

Update documentation on PhoneAccount#EXTRA_SORT_ORDER to make it more
clear what the sorting order is in edge cases.

Make DisconnectCause#REASON_EMULATING_SINGLE_CALL public, since it might
get propogated up to dialer apps.

Fixes: 169153499
Test: docs only
Change-Id: I7f810f909a8a61b422283c3bafcc97307e4d863b
Merged-In: I7f810f909a8a61b422283c3bafcc97307e4d863b

2 files changed, 11 insertions, 5 deletions

diff --git a/telecomm/java/android/telecom/DisconnectCause.java b/telecomm/java/android/telecom/DisconnectCause.java
index f7fe1ba1f998..1472a4ac27bc 100644
--- a/telecomm/java/android/telecom/DisconnectCause.java
+++ b/telecomm/java/android/telecom/DisconnectCause.java
@@ -16,7 +16,6 @@
 
 package android.telecom;
 
-import android.annotation.SystemApi;
 import android.media.ToneGenerator;
 import android.os.Parcel;
 import android.os.Parcelable;
@@ -97,10 +96,7 @@ public final class DisconnectCause implements Parcelable {
      *
      * This reason code is only used for communication between a {@link ConnectionService} and
      * Telecom and should not be surfaced to the user.
-     *
-     * @hide
      */
-    @SystemApi
     public static final String REASON_EMULATING_SINGLE_CALL = "EMULATING_SINGLE_CALL";
 
     /**
diff --git a/telecomm/java/android/telecom/PhoneAccount.java b/telecomm/java/android/telecom/PhoneAccount.java
index cb57df0b2bbc..efdb195343f5 100644
--- a/telecomm/java/android/telecom/PhoneAccount.java
+++ b/telecomm/java/android/telecom/PhoneAccount.java
@@ -27,6 +27,7 @@ import android.net.Uri;
 import android.os.Bundle;
 import android.os.Parcel;
 import android.os.Parcelable;
+import android.telephony.TelephonyManager;
 import android.text.TextUtils;
 
 import java.util.ArrayList;
@@ -51,8 +52,17 @@ public final class PhoneAccount implements Parcelable {
      *
      * This is an extras key set via {@link Builder#setExtras} which determines the order in which
      * {@link PhoneAccount}s from the same {@link ConnectionService} are sorted. The accounts
-     * are sorted by this key via standard lexicographical order, and this ordering is used to
+     * are sorted by this key via standard lexicographical order, (as implemented in
+     * {@link String#compareTo}), and this ordering is used to
      * determine priority when a call can be placed via multiple accounts.
+     *
+     * When multiple {@link PhoneAccount}s are supplied with the same sort order key, no ordering is
+     * guaranteed between those {@link PhoneAccount}s. Additionally, no ordering is guaranteed
+     * between {@link PhoneAccount}s that do not supply this extra, and all such accounts
+     * will be sorted after the accounts that do supply this extra.
+     *
+     * An example of a sort order key is slot index (see {@link TelephonyManager#getSlotIndex()}),
+     * which is the one used by the cell Telephony stack.
      * @hide
      */
     @SystemApi