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

tests/robotests/src/com/android/settings/applications/specialaccess/SystemAlertWindowPreferenceControllerTest.java

@@ -0,0 +1,56 @@
+/*
+ * Copyright (C) 2017 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.google.common.truth.Truth.assertThat;
+
+import android.content.Context;
+
+import com.android.settings.testutils.shadow.ShadowUtils;
+
+import org.junit.Before;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.robolectric.RobolectricTestRunner;
+import org.robolectric.RuntimeEnvironment;
+import org.robolectric.annotation.Config;
+
+@RunWith(RobolectricTestRunner.class)
+@Config(shadows = {ShadowUtils.class})
+public class SystemAlertWindowPreferenceControllerTest {
+
+    private Context mContext;
+    private SystemAlertWindowPreferenceController mController;
+
+    @Before
+    public void setUp() {
+        mContext = RuntimeEnvironment.application;
+        mController = new SystemAlertWindowPreferenceController(mContext, "key");
+    }
+
+    @Test
+    public void systemAlertWindow_byDefault_shouldBeShown() {
+        ShadowUtils.setIsSystemAlertWindowEnabled(true);
+        assertThat(mController.isAvailable()).isTrue();
+    }
+
+    @Test
+    public void systemAlertWindow_lowMemory_shouldNotBeShown() {
+        ShadowUtils.setIsSystemAlertWindowEnabled(false);
+        assertThat(mController.isAvailable()).isFalse();
+    }
+}

tests/robotests/src/com/android/settings/testutils/shadow/ShadowUtils.java

@@ -38,6 +38,7 @@ public class ShadowUtils {
     private static boolean sIsDemoUser;
     private static ComponentName sDeviceOwnerComponentName;
     private static Map<String, String> sAppNameMap;
+    private static boolean sIsSystemAlertWindowEnabled;
 
     @Implementation
     protected static int enforceSameOwner(Context context, int userId) {
@@ -113,4 +114,13 @@ public class ShadowUtils {
         }
         sAppNameMap.put(packageName, appLabel);
     }
+
+    @Implementation
+    protected static boolean isSystemAlertWindowEnabled(Context context) {
+        return sIsSystemAlertWindowEnabled;
+    }
+
+    public static void setIsSystemAlertWindowEnabled(boolean enabled) {
+        sIsSystemAlertWindowEnabled = enabled;
+    }
 }