ThemePicker: Fix ugly black/transparent bar under nav area

Change-Id: I4ba6407ff0f775ac8f694db15b4bd5c2571bdc27

Author: luk1337

AndroidManifest.xml

@@ -28,7 +28,7 @@
             android:name="com.android.customization.picker.CustomizationPickerActivity"
             android:label="@string/app_name"
             android:resizeableActivity="false"
-            android:theme="@style/CustomizationTheme.NoActionBar">
+            android:theme="@style/CustomizationTheme.NoActionBar.CustomizationPicker">
             <intent-filter>
                 <action android:name="android.intent.action.SET_WALLPAPER"/>
 

res/values/styles.xml

@@ -38,7 +38,9 @@
         <item name="android:windowNoTitle">true</item>
         <item name="android:fitsSystemWindows">false</item>
         <item name="android:windowDrawsSystemBarBackgrounds">true</item>
+    </style>
 
+    <style name="CustomizationTheme.NoActionBar.CustomizationPicker" parent="CustomizationTheme.NoActionBar">
         <item name="android:windowBackground">@android:color/transparent</item>
         <item name="android:windowContentOverlay">@null</item>
         <item name="android:windowDisablePreview">true</item>