Listen to mobile data enabled flag change.

The listener is necessary to show/hide the gear icon on top of billing
cycle settings screen as user turn on/off mobile data from QS.

code cleanup: remove dividedCategory

Fix: 28066849
Test: make RunSettinsgRoboTests

Change-Id: I3b7075512042127fd711a8a70a572adfed069502

tests/robotests/src/com/android/settings/datausage/DataUsageListTest.java

@@ -0,0 +1,71 @@
+/*
+ * 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.datausage;
+
+import android.content.Context;
+
+import com.android.settings.SettingsRobolectricTestRunner;
+import com.android.settings.TestConfig;
+import com.android.settingslib.NetworkPolicyEditor;
+
+import org.junit.Before;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.mockito.Mock;
+import org.mockito.MockitoAnnotations;
+import org.robolectric.annotation.Config;
+import org.robolectric.util.ReflectionHelpers;
+
+import static org.mockito.Mockito.doReturn;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.spy;
+import static org.mockito.Mockito.verify;
+
+@RunWith(SettingsRobolectricTestRunner.class)
+@Config(manifest = TestConfig.MANIFEST_PATH, sdk = TestConfig.SDK_VERSION)
+public class DataUsageListTest {
+
+    @Mock
+    private CellDataPreference.DataStateListener mListener;
+    @Mock
+    private TemplatePreference.NetworkServices mNetworkServices;
+    @Mock
+    private Context mContext;
+    private DataUsageList mDataUsageList;
+
+    @Before
+    public void setUp() {
+        MockitoAnnotations.initMocks(this);
+        mNetworkServices.mPolicyEditor = mock(NetworkPolicyEditor.class);
+        mDataUsageList = spy(DataUsageList.class);
+
+        doReturn(mContext).when(mDataUsageList).getContext();
+        ReflectionHelpers.setField(mDataUsageList, "mDataStateListener", mListener);
+        ReflectionHelpers.setField(mDataUsageList, "services", mNetworkServices);
+    }
+
+    @Test
+    public void resumePause_shouldListenUnlistenDataStateChange() {
+        mDataUsageList.onResume();
+
+        verify(mListener).setListener(true, 0, mContext);
+
+        mDataUsageList.onPause();
+
+        verify(mListener).setListener(false, 0, mContext);
+    }
+}