Updating IconCache to maintain a persistent of icons

> IconDB maintains a DB of icons keyed on ComponentName + User
> During loader, icons & labels are loaded first from the DB, and
if the entry doesn't exist, loaded using packageManager
> After the loader completes, IconDB updates any entry which might have
changed, while the launcher was dead.

Change-Id: I7a6021cb6d1ca1e66fa5a0bdd21e1543e0cf66fc
diff --git a/src/com/android/launcher3/LauncherFiles.java b/src/com/android/launcher3/LauncherFiles.java
index fa05365..cedb397 100644
--- a/src/com/android/launcher3/LauncherFiles.java
+++ b/src/com/android/launcher3/LauncherFiles.java
@@ -25,6 +25,7 @@
             WallpaperCropActivity.class.getName();
     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";
 
     public static final List<String> ALL_FILES = Collections.unmodifiableList(Arrays.asList(
             DEFAULT_WALLPAPER_THUMBNAIL,
@@ -36,5 +37,6 @@
             STATS_LOG,
             WALLPAPER_CROP_PREFERENCES_KEY + XML,
             WALLPAPER_IMAGES_DB,
-            WIDGET_PREVIEWS_DB));
+            WIDGET_PREVIEWS_DB,
+            APP_ICONS_DB));
 }