Update Switch track in SwitchPreference on watch

Use white color for switch track, alpha = 0.1 in disable state and alpha
= 0.2 in other states.

Change-Id: I17c570c14ff0d62f2eb18fef3c13df91ac16adc6

core/res/res/drawable/watch_switch_track_material.xml

@@ -1,21 +1,21 @@
 <?xml version="1.0" encoding="utf-8"?>
 <!-- Copyright (C) 2016 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.
 -->
-<!-- Used for the background of switch track for watch switch preference. -->
+
 <selector xmlns:android="http://schemas.android.com/apk/res/android">
-    <item android:state_enabled="false"
-          android:alpha="0.4" android:color="?attr/colorPrimary" />
-    <item android:color="?attr/colorPrimary" />
+    <item android:state_enabled="false">
+        <bitmap android:alpha="0.1" android:src="@drawable/watch_switch_track_mtrl_alpha" />
+    </item>
+    <item>
+        <bitmap android:alpha="0.2" android:src="@drawable/watch_switch_track_mtrl_alpha" />
+    </item>
 </selector>

core/res/res/layout-watch/preference_widget_switch.xml

@@ -24,8 +24,7 @@
     android:thumb="@drawable/watch_switch_thumb_material_anim"
     android:thumbTint="@color/watch_switch_thumb_color_material"
     android:thumbTintMode="multiply"
-    android:track="@drawable/watch_switch_track_mtrl"
-    android:trackTint="@color/watch_switch_track_color_material"
+    android:track="@drawable/watch_switch_track_material"
     android:focusable="false"
     android:clickable="false"
     android:background="@null" />