Implement Android key/value backup

chrome/browser/android/chrome_backup_watcher.h

Index: chrome/browser/android/chrome_backup_watcher.h
diff --git a/chrome/browser/android/chrome_backup_watcher.h b/chrome/browser/android/chrome_backup_watcher.h
new file mode 100644
index 0000000000000000000000000000000000000000..d8eab67721f47b7ba2e059fbd666e05a3e5e31ff
--- /dev/null
+++ b/chrome/browser/android/chrome_backup_watcher.h
@@ -0,0 +1,36 @@
+// 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.
+
+#ifndef CHROME_BROWSER_ANDROID_CHROME_BACKUP_WATCHER_H_
+#define CHROME_BROWSER_ANDROID_CHROME_BACKUP_WATCHER_H_
+
+#include <jni.h>
+
+#include <memory>
+
+#include "base/android/scoped_java_ref.h"
+#include "base/macros.h"
+#include "components/prefs/pref_change_registrar.h"
+
+class Profile;
+
+namespace chrome {
+namespace android {
+
+// Watch the preferences that we back up using Android Backup, so that we can
+// create a new backup whenever any of them change.
+class ChromeBackupWatcher {
+ public:
+  explicit ChromeBackupWatcher(Profile* profile);
+  virtual ~ChromeBackupWatcher();
+
+ private:
+  PrefChangeRegistrar registrar_;
+  base::android::ScopedJavaGlobalRef<jobject> java_watcher_;
+  DISALLOW_COPY_AND_ASSIGN(ChromeBackupWatcher);
+};
+
+}  //  namespace android
+}  //  namespace chrome
+#endif  // CHROME_BROWSER_ANDROID_CHROME_BACKUP_WATCHER_H_