Disable system alert window permissions on low ram devices

Bug: 63697002
Bug: 117832554
Test: adb am start-activity -a
android.settings.action.MANAGE_OVERLAY_PERMISSION
Change-Id: I44c64001cd07fd4934cdc55f455384cebd5c9cfb

src/com/android/settings/applications/specialaccess/SystemAlertWindowPreferenceController.java

@@ -0,0 +1,36 @@
+/*
+ * Copyright (C) 2018 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package com.android.settings.applications.specialaccess;
+
+import static com.android.settings.Utils.isSystemAlertWindowEnabled;
+
+import android.app.ActivityManager;
+import android.content.Context;
+import android.os.Build;
+
+import com.android.settings.core.BasePreferenceController;
+
+public class SystemAlertWindowPreferenceController extends BasePreferenceController {
+    public SystemAlertWindowPreferenceController(Context context, String preferenceKey) {
+        super(context, preferenceKey);
+    }
+
+    @Override
+    public int getAvailabilityStatus() {
+        return isSystemAlertWindowEnabled(mContext)
+                ? AVAILABLE_UNSEARCHABLE : UNSUPPORTED_ON_DEVICE ;
+    }
+}