Fix potential issue where sub info change listener is not registered.

SubscriptionManager#addOnSubscriptionsChangedListener can fail to
register a listener if the TELEPHONY_REGISTRY system service is not up.
Currently this is just silently ignored.

Adding a callback method on the listener to notify the registrant that the
listener failed to be registered, and adding exponential backoff code in
TelecomAccountRegistry to retry registration.

Test: Manual; edited code in Subscriptionmanager to fail the first attempts
to add a listener for TelecomAccountRegistry.  Verified the backoff took
place and registration still occurred for the listener.
Test: Tried to write a mockito test but gave up because this code has
far too many intertwined dependencies and is not inherently testable
Bug: 152217039
Fixes: 153376310

Change-Id: Icf3133cdeca526979cb621f29659b880127b680a
Merged-In: Ib032072dcfd2d3d5e700e380af08b7b3142ebb8e

telephony/java/android/telephony/SubscriptionManager.java

@@ -948,6 +948,18 @@ public class SubscriptionManager {
             if (DBG) log("onSubscriptionsChanged: NOT OVERRIDDEN");
         }
 
+        /**
+         * Callback invoked when {@link SubscriptionManager#addOnSubscriptionsChangedListener(
+         * Executor, OnSubscriptionsChangedListener)} or
+         * {@link SubscriptionManager#addOnSubscriptionsChangedListener(
+         * OnSubscriptionsChangedListener)} fails to complete due to the
+         * {@link Context#TELEPHONY_REGISTRY_SERVICE} being unavailable.
+         * @hide
+         */
+        public void onAddListenerFailed() {
+            Rlog.w(LOG_TAG, "onAddListenerFailed not overridden");
+        }
+
         private void log(String s) {
             Rlog.d(LOG_TAG, s);
         }
@@ -1028,6 +1040,12 @@ public class SubscriptionManager {
         if (telephonyRegistryManager != null) {
             telephonyRegistryManager.addOnSubscriptionsChangedListener(listener,
                     executor);
+        } else {
+            // If the telephony registry isn't available, we will inform the caller on their
+            // listener that it failed so they can try to re-register.
+            loge("addOnSubscriptionsChangedListener: pkgname=" + pkgName + " failed to be added "
+                    + " due to TELEPHONY_REGISTRY_SERVICE being unavailable.");
+            executor.execute(() -> listener.onAddListenerFailed());
         }
     }