Send a command to the wallpaper when re-applying it

We don't set a wallpaper component again if it's the one
already set, so we're now sending it a command notifying
of this in case the wallpaper needs to reload or apply
settings.

Bug: 147677688
Test: atest WallpaperManagerServiceTests
Change-Id: If65671287ba3270933b75771a8c1c65c5ff0216a

core/java/android/app/WallpaperManager.java

@@ -177,6 +177,13 @@ public class WallpaperManager {
      */
     public static final String COMMAND_DROP = "android.home.drop";
 
+    /**
+     * Command for {@link #sendWallpaperCommand}: reported when the wallpaper that was already
+     * set is re-applied by the user.
+     * @hide
+     */
+    public static final String COMMAND_REAPPLY = "android.wallpaper.reapply";
+
     /**
      * Extra passed back from setWallpaper() giving the new wallpaper's assigned ID.
      * @hide