Extends SeekBarPreference to add labels and callbacks

Adds title, left and right labels to the SeekBarPreference. Also adds
a listener for the seek stop event.

Bug: 146004827
Test: make RunSettingsRoboTests ROBOTEST_FILTER=GestureNavigationSeekBarPreferenceTest

Change-Id: I0ecca4e92cfc52abb8bb975b710f72f75ed5b50d

res/layout/preference_gesture_navigation_slider.xml

@@ -0,0 +1,81 @@
+<?xml version="1.0" encoding="utf-8"?>
+
+<!--
+  ~ Copyright (C) 2019 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
+  -->
+
+<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
+    android:layout_width="match_parent"
+    android:gravity="center_vertical"
+    android:layout_height="wrap_content"
+    android:orientation="vertical"
+    android:paddingStart="56dp"
+    android:paddingEnd="8dp"
+    android:paddingTop="16dp"
+    android:paddingBottom="8dp">
+
+    <TextView
+        android:id="@android:id/title"
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:layout_marginStart="16dp"
+        android:layout_alignParentTop="true"
+        android:ellipsize="marquee"
+        android:fadingEdge="horizontal"
+        android:singleLine="true"
+        android:textAppearance="@android:style/TextAppearance.Material.Subhead"
+        android:textColor="?android:attr/textColorPrimary" />
+
+    <SeekBar
+        android:id="@*android:id/seekbar"
+        android:layout_below="@android:id/title"
+        android:layout_gravity="center_vertical"
+        android:layout_width="match_parent"
+        android:layout_height="70dp"
+        android:layout_marginTop="-20dp"
+        android:layout_marginBottom="-28dp"
+        style="@android:style/Widget.Material.SeekBar.Discrete" />
+
+    <LinearLayout
+        android:layout_width="match_parent"
+        android:layout_height="wrap_content"
+        android:layout_below="@*android:id/seekbar"
+        android:paddingBottom="8dp"
+        android:orientation="horizontal">
+
+        <TextView
+            android:id="@android:id/text1"
+            android:layout_marginStart="16dp"
+            android:layout_width="0dp"
+            android:layout_height="wrap_content"
+            android:layout_gravity="start|top"
+            android:gravity="start"
+            android:text="@string/low_label"
+            android:layout_weight="1"/>
+
+        <TextView
+            android:id="@android:id/text2"
+            android:layout_marginEnd="16dp"
+            android:layout_width="0dp"
+            android:layout_height="wrap_content"
+            android:layout_gravity="end|top"
+            android:gravity="end"
+            android:text="@string/high_label"
+            android:layout_weight="1"/>
+
+    </LinearLayout>
+
+</RelativeLayout>
+