Add infra for battery tip

This cl adds the basic structure for battery tip:
1. BaseBatteryTip: Model class to represent the tip and build
preference and dialog
2. SummaryTip: Display a general battery summary(i.e. your battery
is good..)
3. BatteryTipLoader: AsyncLoader to load the battery tips.
4. BatteryTipPreferenceController: preference controller for
preference group to display battery tips

This cl also:
1. Remove the anomaly code in PowerUsageSummary and we will add it
to app restriction in future.
2. Add preference_category_no_title.xml to avoid the extra 32dp
blank at the top.

Bug: 70570352
Test: RunSettingsRoboTests
Change-Id: If91a553888e2eb91d55fb1d0d7bbea69652f144c

src/com/android/settings/fuelgauge/batterytip/BatteryTipLoader.java

@@ -0,0 +1,58 @@
+/*
+ * 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.fuelgauge.batterytip;
+
+import android.content.Context;
+
+import com.android.internal.os.BatteryStatsHelper;
+import com.android.settings.fuelgauge.batterytip.tips.BatteryTip;
+import com.android.settings.fuelgauge.batterytip.tips.SummaryTip;
+import com.android.settingslib.utils.AsyncLoader;
+
+import java.util.ArrayList;
+import java.util.List;
+
+/**
+ * Loader to compute and return a battery tip list. It will always return a full length list even
+ * though some tips may have state {@code BaseBatteryTip.StateType.INVISIBLE}.
+ */
+public class BatteryTipLoader extends AsyncLoader<List<BatteryTip>> {
+    private static final String TAG = "BatteryTipLoader";
+
+    private static final boolean USE_FAKE_DATA = false;
+
+    private BatteryStatsHelper mBatteryStatsHelper;
+
+    public BatteryTipLoader(Context context, BatteryStatsHelper batteryStatsHelper) {
+        super(context);
+        mBatteryStatsHelper = batteryStatsHelper;
+    }
+
+    @Override
+    public List<BatteryTip> loadInBackground() {
+        List<BatteryTip> tips = new ArrayList<>();
+
+        //TODO(b/70570352): add battery tip detectors
+        tips.add(new SummaryTip(BatteryTip.StateType.NEW));
+        return tips;
+    }
+
+    @Override
+    protected void onDiscardResult(List<BatteryTip> result) {
+    }
+
+}