Make fallback home a bit more graceful.

This change switches the theme used so we show through to the
wallpaper (instead of showing black), which makes initial device
startup less jarring.

Bug: 26458596
Change-Id: I73c7f1cf25dd21cb4a4012fb62f8828eb46a8368

AndroidManifest.xml

@@ -2258,7 +2258,7 @@
         <!-- Triggered when user-selected home app isn't encryption aware -->
         <activity android:name=".FallbackHome"
                   android:excludeFromRecents="true"
-                  android:theme="@android:style/Theme.Translucent.NoTitleBar">
+                  android:theme="@style/FallbackHome">
             <intent-filter android:priority="-1000">
                 <action android:name="android.intent.action.MAIN" />
                 <category android:name="android.intent.category.HOME" />

res/values/themes.xml

@@ -298,4 +298,10 @@
         <item name="suwMarginSides">@dimen/suw_layout_margin_sides</item>
     </style>
 
+    <style name="FallbackHome" parent="@android:style/Theme.Material.Wallpaper.NoTitleBar">
+        <item name="android:windowTranslucentStatus">true</item>
+        <item name="android:windowTranslucentNavigation">true</item>
+        <item name="android:windowAnimationStyle">@null</item>
+    </style>
+
 </resources>