Add Volume panel

Volume panel hosts each volume stream, including:
- Media volume
- Call Volume
- Ring volume
- Alarm volume

Change-Id: I1801d10d2304c57615e9499386c638c74ffcd7c3
Screenshot: https://screenshot.googleplex.com/m764j65ECto
Bug: 117804161
Test: Manual app
Test: robolectric

tests/robotests/src/com/android/settings/panel/VolumePanelTest.java

@@ -0,0 +1,58 @@
+/*
+ * 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.panel;
+
+import static com.google.common.truth.Truth.assertThat;
+
+import android.net.Uri;
+
+import com.android.settings.slices.CustomSliceRegistry;
+import com.android.settings.testutils.SettingsRobolectricTestRunner;
+
+import org.junit.Before;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.robolectric.RuntimeEnvironment;
+
+import java.util.List;
+
+@RunWith(SettingsRobolectricTestRunner.class)
+public class VolumePanelTest {
+
+    private VolumePanel mPanel;
+
+    @Before
+    public void setUp() {
+        mPanel = VolumePanel.create(RuntimeEnvironment.application);
+    }
+
+    @Test
+    public void getSlices_containsNecessarySlices() {
+        final List<Uri> uris = mPanel.getSlices();
+
+        assertThat(uris).containsExactly(
+                CustomSliceRegistry.VOLUME_CALL_URI,
+                CustomSliceRegistry.VOLUME_MEDIA_URI,
+                CustomSliceRegistry.VOLUME_RINGER_URI,
+                CustomSliceRegistry.VOLUME_ALARM_URI);
+    }
+
+    @Test
+    public void getSeeMoreIntent_notNull() {
+        assertThat(mPanel.getSeeMoreIntent()).isNotNull();
+    }
+}