Adding migration Clings. (Bug 11973614)

- Refactoring Launcher cling code out to LauncherClings.

Change-Id: Iff4f84f5b8bfeb69b1be0b4802022c3eb20b6f2c
diff --git a/src/com/android/launcher3/LauncherModel.java b/src/com/android/launcher3/LauncherModel.java
index b2cfb24..498d91a 100644
--- a/src/com/android/launcher3/LauncherModel.java
+++ b/src/com/android/launcher3/LauncherModel.java
@@ -77,7 +77,9 @@
 
     private static final int ITEMS_CHUNK = 6; // batch size for the workspace icons
     private static final long INVALID_SCREEN_ID = -1L;
+
     private final boolean mAppsCanBeOnRemoveableStorage;
+    private final boolean mOldContentProviderExists;
 
     private final LauncherAppState mApp;
     private final Object mLock = new Object();
@@ -181,9 +183,12 @@
     }
 
     LauncherModel(LauncherAppState app, IconCache iconCache, AppFilter appFilter) {
-        final Context context = app.getContext();
+        Context context = app.getContext();
+        ContentResolver contentResolver = context.getContentResolver();
 
         mAppsCanBeOnRemoveableStorage = Environment.isExternalStorageRemovable();
+        mOldContentProviderExists = (contentResolver.acquireContentProviderClient(
+                LauncherSettings.Favorites.OLD_CONTENT_URI) != null);
         mApp = app;
         mBgAllAppsList = new AllAppsList(iconCache, appFilter);
         mIconCache = iconCache;
@@ -218,6 +223,10 @@
         }
     }
 
+    boolean canMigrateFromOldLauncherDb() {
+        return mOldContentProviderExists;
+    }
+
     static boolean findNextAvailableIconSpaceInScreen(ArrayList<ItemInfo> items, int[] xy,
                                  long screen) {
         LauncherAppState app = LauncherAppState.getInstance();
@@ -1651,7 +1660,7 @@
             }
         }
 
-        /** Returns whether this is an upgradge path */
+        /** Returns whether this is an upgrade path */
         private boolean loadWorkspace() {
             // Log to disk
             Launcher.addDumpLog(TAG, "11683562 - loadWorkspace()", true);