Remove duplicate preferences in Accessibility settings.

- addPreferencesFromResource() call has been added to
InstrumentedPreferenceFragment, and hence sub-class should not call it
again.

Change-Id: Ia016d9d407ac3f838c962d1ced585647382a051a
Fixes: 68820835
Test: make RunSettingsRoboTests

tests/robotests/src/com/android/settings/accessibility/ToggleFeaturePreferenceFragmentTest.java

@@ -0,0 +1,99 @@
+/*
+ * 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.accessibility;
+
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.spy;
+import static org.mockito.Mockito.verify;
+
+import android.os.Bundle;
+import android.support.annotation.XmlRes;
+import android.view.LayoutInflater;
+import android.view.View;
+import android.view.ViewGroup;
+
+import com.android.settings.R;
+import com.android.settings.TestConfig;
+import com.android.settings.testutils.SettingsRobolectricTestRunner;
+import com.android.settings.testutils.shadow.SettingsShadowResources;
+import com.android.settings.widget.SwitchBar;
+
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.robolectric.annotation.Config;
+import org.robolectric.util.FragmentTestUtil;
+
+@RunWith(SettingsRobolectricTestRunner.class)
+@Config(manifest = TestConfig.MANIFEST_PATH, sdk = TestConfig.SDK_VERSION,
+        shadows = {
+                SettingsShadowResources.class,
+                SettingsShadowResources.SettingsShadowTheme.class,
+        })
+public class ToggleFeaturePreferenceFragmentTest {
+
+    private ToggleFeaturePreferenceFragmentTestable mFragment;
+
+    @Test
+    public void createFragment_shouldOnlyAddPreferencesOnce() {
+        mFragment = spy(new ToggleFeaturePreferenceFragmentTestable());
+
+        FragmentTestUtil.startFragment(mFragment);
+
+        // execute exactly once
+        verify(mFragment).addPreferencesFromResource(R.xml.placeholder_prefs);
+    }
+
+
+    public static class ToggleFeaturePreferenceFragmentTestable
+            extends ToggleFeaturePreferenceFragment {
+
+        @Override
+        protected void onPreferenceToggled(String preferenceKey, boolean enabled) {}
+
+        @Override
+        public int getMetricsCategory() {
+            return 0;
+        }
+
+        @Override
+        public int getPreferenceScreenResId() {
+            return R.xml.placeholder_prefs;
+        }
+
+        @Override
+        public View onCreateView(LayoutInflater inflater, ViewGroup container,
+                Bundle savedInstanceState) {
+            return mock(View.class);
+        }
+
+        @Override
+        public void addPreferencesFromResource(@XmlRes int preferencesResId) {
+            // do nothing
+        }
+
+        @Override
+        public void onViewCreated(View view, Bundle savedInstanceState) {
+            // do nothing
+        }
+
+        @Override
+        public void onActivityCreated(Bundle savedInstanceState) {
+            mSwitchBar = mock(SwitchBar.class);
+            super.onActivityCreated(savedInstanceState);
+        }
+    }
+}