Implement Android key/value backup

chrome/android/java/src/org/chromium/chrome/browser/ChromeBackupWatcher.java

+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package org.chromium.chrome.browser;
+
+import android.app.backup.BackupManager;
+import android.content.Context;
+import android.content.SharedPreferences;
+
+import org.chromium.base.ContextUtils;
+import org.chromium.base.VisibleForTesting;
+import org.chromium.base.annotations.CalledByNative;
+import org.chromium.base.annotations.JNINamespace;
+import org.chromium.components.signin.ChromeSigninController;
+
+/**
+ * Class for watching for changes to the Android preferences that are backed up using Android
+ * key/value backup.
+ */
+@JNINamespace("chrome::android")
+public class ChromeBackupWatcher {
+    private BackupManager mBackupManager;
+
+    @VisibleForTesting
+    @CalledByNative
+    static ChromeBackupWatcher createChromeBackupWatcher() {
+        return new ChromeBackupWatcher();
+    }
+
+    private ChromeBackupWatcher() {
+        Context context = ContextUtils.getApplicationContext();
+        if (context == null) return;
+
+        mBackupManager = new BackupManager(context);
+        // Watch the Java preferences that are backed up.
+        SharedPreferences sharedPrefs = ContextUtils.getAppSharedPreferences();
+        sharedPrefs.registerOnSharedPreferenceChangeListener(
+                new SharedPreferences.OnSharedPreferenceChangeListener() {
+
+                    @Override
+                    public void onSharedPreferenceChanged(
+                            SharedPreferences sharedPreferences, String key) {
+                        // Update the backup if the user id or any of the backed up Android
+                        // preferences change.
+                        if (key.equals(ChromeSigninController.SIGNED_IN_ACCOUNT_KEY)) {
+                            onBackupPrefsChanged();
+                            return;
+                        }
+                        for (String pref : ChromeBackupAgent.BACKUP_ANDROID_BOOL_PREFS) {
+                            if (key.equals(pref)) {
+                                onBackupPrefsChanged();
+                                return;
+                            }
+                        }
+                    }
+
+                });
+    }
+
+    @CalledByNative
+    private void onBackupPrefsChanged() {
+        mBackupManager.dataChanged();
+    }
+}