Convert BatterySaverButton controller to Slice compatible.

- Update preference key to match the key defined in SettingsSlicesContract
- Model TwoStateButtonPreference similar to TwoStatePreference (add
  setChecked, isChecked method)
- Remove TwoStateButtonPreferenceController entirely because all methods
  are moved into Preference directly for better encapsulation.
- Make BatterySaverButtonPrefController direclty implement
  TogglePreferenceController. It was not possible before because the
  interface between TwoStateButtonPreferene is too different from
  TwoStatePreference.

Bug: 80106671
Test: robotests
Change-Id: Ib72807dcf1b36e959e08df8d80538c3f9f79b76d

tests/robotests/src/com/android/settings/widget/TwoStateButtonPreferenceTest.java

@@ -0,0 +1,98 @@
+/*
+ * 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.widget;
+
+import static com.google.common.truth.Truth.assertThat;
+import static org.mockito.Mockito.spy;
+import static org.mockito.Mockito.verify;
+
+import android.content.Context;
+import android.view.View;
+import android.widget.Button;
+
+import com.android.settings.R;
+import com.android.settings.testutils.SettingsRobolectricTestRunner;
+
+import org.junit.Before;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.mockito.MockitoAnnotations;
+import org.robolectric.RuntimeEnvironment;
+import org.robolectric.util.ReflectionHelpers;
+
+@RunWith(SettingsRobolectricTestRunner.class)
+public class TwoStateButtonPreferenceTest {
+
+    private TwoStateButtonPreference mPreference;
+    private Context mContext;
+    private Button mButtonOn;
+    private Button mButtonOff;
+
+    @Before
+    public void setUp() {
+        MockitoAnnotations.initMocks(this);
+        mContext = spy(RuntimeEnvironment.application);
+        mPreference = spy(new TwoStateButtonPreference(mContext, null /* AttributeSet */));
+        mButtonOn = new Button(mContext);
+        mButtonOn.setId(R.id.state_on_button);
+        mButtonOff = new Button(mContext);
+        mButtonOff.setId(R.id.state_off_button);
+        ReflectionHelpers.setField(mPreference, "mButtonOn", mButtonOn);
+        ReflectionHelpers.setField(mPreference, "mButtonOff", mButtonOff);
+    }
+
+    @Test
+    public void testSetButtonVisibility_stateOn_onlyShowButtonOn() {
+        mPreference.setChecked(true /* stateOn */);
+
+        assertThat(mButtonOn.getVisibility()).isEqualTo(View.GONE);
+        assertThat(mButtonOff.getVisibility()).isEqualTo(View.VISIBLE);
+    }
+
+    @Test
+    public void testSetButtonVisibility_stateOff_onlyShowButtonOff() {
+        mPreference.setChecked(false /* stateOn */);
+
+        assertThat(mButtonOn.getVisibility()).isEqualTo(View.VISIBLE);
+        assertThat(mButtonOff.getVisibility()).isEqualTo(View.GONE);
+    }
+
+    @Test
+    public void testSetButtonEnabled_enabled_buttonEnabled() {
+        mPreference.setButtonEnabled(true /* enabled */);
+
+        assertThat(mButtonOn.isEnabled()).isTrue();
+        assertThat(mButtonOff.isEnabled()).isTrue();
+    }
+
+    @Test
+    public void testSetButtonEnabled_disabled_buttonDisabled() {
+        mPreference.setButtonEnabled(false /* enabled */);
+
+        assertThat(mButtonOn.isEnabled()).isFalse();
+        assertThat(mButtonOff.isEnabled()).isFalse();
+    }
+
+    @Test
+    public void onClick_shouldPropagateChangeToListener() {
+        mPreference.onClick(mButtonOn);
+        verify(mPreference).callChangeListener(true);
+
+        mPreference.onClick(mButtonOff);
+        verify(mPreference).callChangeListener(false);
+    }
+}