Ask to enable touch exploration only the first time it enables the feature.

1. Now we are asking the user to grant permission to the service to enable
   touch exploration only the first time this service is enabled. If the
   service was uninstalled and then later installed we ask the user again.
   This avoids the scenario in which rebooting the device or upgrading an
   accessibility service leaves the device in a state in which the user
   cannot interact with.

bug:6582088

Change-Id: I51d24e4892b3b48c9fb11dfb09ec1118502ba526

Author: sganov

core/java/android/provider/Settings.java

@@ -2885,6 +2885,15 @@ public static final String getBluetoothInputDevicePriorityKey(String address) {
         public static final String ENABLED_ACCESSIBILITY_SERVICES =
             "enabled_accessibility_services";
 
+        /**
+         * List of the accessibility services to which the user has graned
+         * permission to put the device into touch exploration mode.
+         *
+         * @hide
+         */
+        public static final String TOUCH_EXPLORATION_GRANTED_ACCESSIBILITY_SERVICES =
+            "touch_exploration_granted_accessibility_services";
+
         /**
          * Whether to speak passwords while in accessibility mode.
          */
@@ -4292,6 +4301,7 @@ public static final String getBluetoothInputDevicePriorityKey(String address) {
             ACCESSIBILITY_SCRIPT_INJECTION,
             BACKUP_AUTO_RESTORE,
             ENABLED_ACCESSIBILITY_SERVICES,
+            TOUCH_EXPLORATION_GRANTED_ACCESSIBILITY_SERVICES,
             TOUCH_EXPLORATION_ENABLED,
             ACCESSIBILITY_ENABLED,
             ACCESSIBILITY_SPEAK_PASSWORD,