Start backing up wallpaper

This CL does the following:
   + adds an AbsoluteFileBackupHelper class for managing backup of files
     known by absolute path, not based off of the app's getFilesDir() root
   + bumps up the collection interval from its testing-only default of 1 second
     to 3 minutes
   + adds a SystemBackupAgent class to the main system package and names it as
     the android:backupAgent for the main OS package.  Right now this agent
     only backs up & restores the wallpaper file.
   + amend the Wallpaper Service to inform the Backup Manager when the wallpaper
     changes.

On the subject of the 3-minute collection interval before the backup actually
occurs:  this can be short-circuited from an adb shell.  Running the command
'bmgr run' will cause the Backup Manager to kick off any pending backup
operations immediately.

2 files changed, 15 insertions, 4 deletions

diff --git a/services/java/com/android/server/BackupManagerService.java b/services/java/com/android/server/BackupManagerService.java
index fdd4617..efa6179 100644
--- a/services/java/com/android/server/BackupManagerService.java
+++ b/services/java/com/android/server/BackupManagerService.java
@@ -76,8 +76,7 @@ class BackupManagerService extends IBackupManager.Stub {
     private static final boolean DEBUG = true;
 
     // Default time to wait after data changes before we back up the data
-    private static final long COLLECTION_INTERVAL = 1000;
-    //private static final long COLLECTION_INTERVAL = 3 * 60 * 1000;
+    private static final long COLLECTION_INTERVAL = 3 * 60 * 1000;
 
     private static final int MSG_RUN_BACKUP = 1;
     private static final int MSG_RUN_FULL_BACKUP = 2;
@@ -360,7 +359,8 @@ class BackupManagerService extends IBackupManager.Stub {
         if (DEBUG) {
             Log.v(TAG, "Adding " + targetPkgs.size() + " backup participants:");
             for (PackageInfo p : targetPkgs) {
-                Log.v(TAG, "    " + p + " agent=" + p.applicationInfo.backupAgentName);
+                Log.v(TAG, "    " + p + " agent=" + p.applicationInfo.backupAgentName
+                        + " uid=" + p.applicationInfo.uid);
             }
         }
 
diff --git a/services/java/com/android/server/WallpaperService.java b/services/java/com/android/server/WallpaperService.java
index 5532894..d921baf 100644
--- a/services/java/com/android/server/WallpaperService.java
+++ b/services/java/com/android/server/WallpaperService.java
@@ -18,8 +18,10 @@ package com.android.server;
 
 import static android.os.FileObserver.*;
 import static android.os.ParcelFileDescriptor.*;
+
 import android.app.IWallpaperService;
 import android.app.IWallpaperServiceCallback;
+import android.backup.BackupManager;
 import android.content.Context;
 import android.content.Intent;
 import android.content.SharedPreferences;
@@ -154,7 +156,16 @@ class WallpaperService extends IWallpaperService.Stub {
     public ParcelFileDescriptor setWallpaper() {
         checkPermission(android.Manifest.permission.SET_WALLPAPER);
         try {
-            return ParcelFileDescriptor.open(WALLPAPER_FILE, MODE_CREATE|MODE_READ_WRITE);
+            ParcelFileDescriptor fd = ParcelFileDescriptor.open(WALLPAPER_FILE,
+                    MODE_CREATE|MODE_READ_WRITE);
+
+            // changing the wallpaper means we'll need to back up the new one
+            long origId = Binder.clearCallingIdentity();
+            BackupManager bm = new BackupManager(mContext);
+            bm.dataChanged();
+            Binder.restoreCallingIdentity(origId);
+
+            return fd;
         } catch (FileNotFoundException e) {
             if (Config.LOGD) Log.d(TAG, "Error setting wallpaper", e);
         }