AI 143776: am: CL 143622 Correctly startListening() for widget updates when first boot completes.
  During the first boot upgrade, LauncherProvider will deleteHost() to clear out any old appWidgetId bindings.  During the first boot, Launcher calls AppWidgetHost.startListening() to watch for widget updates.  It also calls loadUserItems(), which loads data from LauncherProvider, triggering the database creation and deleteHost() call.  Because deleteHost() removes any existing callbacks, any future widget updates are dropped on the floor.  (This can currently be solved by rebooting, because there isn't an upgrade on subsequent boots.)
  This bug was particularly evident on vfpioneer-userdebug builds, as there aren't any configuration changes that cause Launcher to be destroyed and recreated.  (When destroyed and recreated, we startListening() again, and LauncherProvider doesn't call deleteHost().)
  To handle this special case, Launcher creates a ContentObserver pointing at a specific URI, which the LauncherProvider notifies when the AppWidgetHost is reset through deleteHost(), allowing Launcher to correctly startListening() again.
  Original author: jsharkey
  Merged from: //branches/cupcake/...

Automated import of CL 143776
diff --git a/src/com/android/launcher/Launcher.java b/src/com/android/launcher/Launcher.java
index 7b7802e..7dd3418 100644
--- a/src/com/android/launcher/Launcher.java
+++ b/src/com/android/launcher/Launcher.java
@@ -168,6 +168,7 @@
 
     private final BroadcastReceiver mApplicationsReceiver = new ApplicationsIntentReceiver();
     private final ContentObserver mObserver = new FavoritesChangeObserver();
+    private final ContentObserver mAppWidgetResetObserver = new AppWidgetResetObserver();
 
     private LayoutInflater mInflater;
 
@@ -826,6 +827,7 @@
         sModel.abortLoaders();
 
         getContentResolver().unregisterContentObserver(mObserver);
+        getContentResolver().unregisterContentObserver(mAppWidgetResetObserver);
         unregisterReceiver(mApplicationsReceiver);
     }
 
@@ -1156,6 +1158,7 @@
     private void registerContentObservers() {
         ContentResolver resolver = getContentResolver();
         resolver.registerContentObserver(LauncherSettings.Favorites.CONTENT_URI, true, mObserver);
+        resolver.registerContentObserver(LauncherProvider.CONTENT_APPWIDGET_RESET_URI, true, mAppWidgetResetObserver);
     }
 
     @Override
@@ -1221,6 +1224,16 @@
         sModel.loadUserItems(false, this, false, false);
     }
 
+    /**
+     * When reset, we handle by calling {@link AppWidgetHost#startListening()}
+     * to make sure our callbacks are set correctly.
+     */
+    private void onAppWidgetReset() {
+        if (mAppWidgetHost != null) {
+            mAppWidgetHost.startListening();
+        }
+    }
+
     void onDesktopItemsLoaded() {
         if (mDestroyed) return;
         bindDesktopItems();
@@ -1878,6 +1891,21 @@
     }
 
     /**
+     * Receives notifications when the {@link AppWidgetHost} has been reset,
+     * usually only when the {@link LauncherProvider} database is first created.
+     */
+    private class AppWidgetResetObserver extends ContentObserver {
+        public AppWidgetResetObserver() {
+            super(new Handler());
+        }
+
+        @Override
+        public void onChange(boolean selfChange) {
+            onAppWidgetReset();
+        }
+    }
+
+    /**
      * Receives intents from other applications to change the wallpaper.
      */
     private static class WallpaperIntentReceiver extends BroadcastReceiver {