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

api/current.txt

@@ -45977,6 +45977,7 @@ package android.telecom {
     field public static final int MISSED = 5; // 0x5
     field public static final int OTHER = 9; // 0x9
     field public static final String REASON_EMERGENCY_CALL_PLACED = "REASON_EMERGENCY_CALL_PLACED";
+    field public static final String REASON_EMULATING_SINGLE_CALL = "EMULATING_SINGLE_CALL";
     field public static final String REASON_IMS_ACCESS_BLOCKED = "REASON_IMS_ACCESS_BLOCKED";
     field public static final String REASON_WIFI_ON_BUT_WFC_OFF = "REASON_WIFI_ON_BUT_WFC_OFF";
     field public static final int REJECTED = 6; // 0x6

api/system-current.txt

@@ -10270,10 +10270,6 @@ package android.telecom {
     method public final void addExistingConnection(@NonNull android.telecom.PhoneAccountHandle, @NonNull android.telecom.Connection, @NonNull android.telecom.Conference);
   }
 
-  public final class DisconnectCause implements android.os.Parcelable {
-    field public static final String REASON_EMULATING_SINGLE_CALL = "EMULATING_SINGLE_CALL";
-  }
-
   public abstract class InCallService extends android.app.Service {
     method @Deprecated public android.telecom.Phone getPhone();
     method @Deprecated public void onPhoneCreated(android.telecom.Phone);

non-updatable-api/current.txt

@@ -44145,6 +44145,7 @@ package android.telecom {
     field public static final int MISSED = 5; // 0x5
     field public static final int OTHER = 9; // 0x9
     field public static final String REASON_EMERGENCY_CALL_PLACED = "REASON_EMERGENCY_CALL_PLACED";
+    field public static final String REASON_EMULATING_SINGLE_CALL = "EMULATING_SINGLE_CALL";
     field public static final String REASON_IMS_ACCESS_BLOCKED = "REASON_IMS_ACCESS_BLOCKED";
     field public static final String REASON_WIFI_ON_BUT_WFC_OFF = "REASON_WIFI_ON_BUT_WFC_OFF";
     field public static final int REJECTED = 6; // 0x6

non-updatable-api/system-current.txt

@@ -9152,10 +9152,6 @@ package android.telecom {
     method public final void addExistingConnection(@NonNull android.telecom.PhoneAccountHandle, @NonNull android.telecom.Connection, @NonNull android.telecom.Conference);
   }
 
-  public final class DisconnectCause implements android.os.Parcelable {
-    field public static final String REASON_EMULATING_SINGLE_CALL = "EMULATING_SINGLE_CALL";
-  }
-
   public abstract class InCallService extends android.app.Service {
     method @Deprecated public android.telecom.Phone getPhone();
     method @Deprecated public void onPhoneCreated(android.telecom.Phone);

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";
 
     /**

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