Removing all dependencies of launcher code on wallpaper-picker

> WallpaperPicker can still depend on launcher code, but not the
other way round.

Change-Id: I93a07f985c3955c638a68a5fad9c09b184a879b9
diff --git a/src/com/android/launcher3/LauncherFiles.java b/src/com/android/launcher3/LauncherFiles.java
index ce277c1..699cb37 100644
--- a/src/com/android/launcher3/LauncherFiles.java
+++ b/src/com/android/launcher3/LauncherFiles.java
@@ -20,7 +20,8 @@
     public static final String LAUNCHER_PREFERENCES = "launcher.preferences";
     public static final String SHARED_PREFERENCES_KEY = "com.android.launcher3.prefs";
     public static final String WALLPAPER_CROP_PREFERENCES_KEY =
-            WallpaperCropActivity.class.getName();
+            "com.android.launcher3.WallpaperCropActivity";
+
     public static final String WALLPAPER_IMAGES_DB = "saved_wallpaper_images.db";
     public static final String WIDGET_PREVIEWS_DB = "widgetpreviews.db";
     public static final String APP_ICONS_DB = "app_icons.db";