*DRAFT* Move MediaDeviceIDSalt from chrome/ to components/ and use it in Android WebView.

chrome/browser/media/media_device_id_salt.cc

-// Copyright 2013 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.
-#include "chrome/browser/media/media_device_id_salt.h"
-
-#include "base/base64.h"
-#include "base/rand_util.h"
-#include "chrome/browser/profiles/profile_io_data.h"
-#include "chrome/common/pref_names.h"
-#include "components/prefs/pref_service.h"
-#include "content/public/browser/browser_thread.h"
-
-using content::BrowserThread;
-
-namespace {
-
-std::string CreateSalt() {
-  std::string salt;
-  base::Base64Encode(base::RandBytesAsString(16), &salt);
-  DCHECK(!salt.empty());
-  return salt;
-}
-
-}  // namespace
-
-MediaDeviceIDSalt::MediaDeviceIDSalt(PrefService* pref_service,
-                                     bool incognito) {
-  DCHECK_CURRENTLY_ON(BrowserThread::UI);
-
-  if (incognito) {
-    incognito_salt_ = CreateSalt();
-    return;
-  }
-
-  media_device_id_salt_.Init(prefs::kMediaDeviceIdSalt, pref_service);
-  if (media_device_id_salt_.GetValue().empty())
-    media_device_id_salt_.SetValue(CreateSalt());
-
-  media_device_id_salt_.MoveToThread(
-      BrowserThread::GetMessageLoopProxyForThread(BrowserThread::IO));
-}
-
-MediaDeviceIDSalt::~MediaDeviceIDSalt() {
-}
-
-void MediaDeviceIDSalt::ShutdownOnUIThread() {
-  DCHECK_CURRENTLY_ON(BrowserThread::UI);
-  if (incognito_salt_.empty())
-    media_device_id_salt_.Destroy();
-}
-
-std::string MediaDeviceIDSalt::GetSalt() const {
-  DCHECK_CURRENTLY_ON(BrowserThread::IO);
-  if (incognito_salt_.size())
-    return incognito_salt_;
-  return media_device_id_salt_.GetValue();
-}
-
-void MediaDeviceIDSalt::RegisterProfilePrefs(
-    user_prefs::PrefRegistrySyncable* registry) {
-  registry->RegisterStringPref(prefs::kMediaDeviceIdSalt, std::string());
-}
-
-void MediaDeviceIDSalt::Reset(PrefService* pref_service) {
-  pref_service->SetString(prefs::kMediaDeviceIdSalt,
-                          CreateSalt());
-}