Enable notification permission enforcement

This change will guard posting notifications with a new
"android.permission.POST_NOTIFICATIONS" permission introcuded as part of
Android T.

This permission is marked "dangerous" and will require both declaring
usage of the permission in AndroidManifest.xml as well as showing a
runtime prompt to the user in order to be granted the permission.

Packages which are not granted the permission will have their
notifications silently dropped.

Test: atest Cts*
Bug: 194833441

Change-Id: I274738d4d4c3b09902844708327feb2d1d367307

packages/SettingsProvider/src/com/android/providers/settings/SettingsProvider.java

@@ -3624,7 +3624,7 @@ public class SettingsProvider extends ContentProvider {
         }
 
         private final class UpgradeController {
-            private static final int SETTINGS_VERSION = 208;
+            private static final int SETTINGS_VERSION = 209;
 
             private final int mUserId;
 
@@ -5497,6 +5497,20 @@ public class SettingsProvider extends ContentProvider {
                     currentVersion = 208;
                 }
 
+                if (currentVersion == 208) {
+                    // Version 208: Enable enforcement of
+                    // android.Manifest.permission#POST_NOTIFICATIONS in order for applications
+                    // to post notifications.
+                    final SettingsState secureSettings = getSecureSettingsLocked(userId);
+                    secureSettings.insertSettingLocked(
+                            Secure.NOTIFICATION_PERMISSION_ENABLED,
+                            /* enabled= */" 1",
+                            /* tag= */ null,
+                            /* makeDefault= */ false,
+                            SettingsState.SYSTEM_PACKAGE_NAME);
+                    currentVersion = 209;
+                }
+
                 // vXXX: Add new settings above this point.
 
                 if (currentVersion != newVersion) {