Implement a salt for MediaSource IDs that can be cleared by a user.

content/browser/media_devices_monitor.cc

-// Copyright (c) 2012 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 "content/public/browser/media_devices_monitor.h"
-
-#include "content/browser/browser_main_loop.h"
-#include "content/browser/renderer_host/media/media_stream_manager.h"
-#include "content/public/browser/browser_thread.h"
-
-namespace content {
-namespace {
-void EnsureMonitorCaptureDevicesInternal(
-    MediaStreamManager* media_stream_manager) {
-  media_stream_manager->EnumerateDevices(
-      NULL, -1, -1, -1, MEDIA_DEVICE_AUDIO_CAPTURE, GURL());
-}
-}
-
-void EnsureMonitorCaptureDevices() {
-  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
-
-  BrowserThread::PostTask(
-      BrowserThread::IO, FROM_HERE,
-      base::Bind(&EnsureMonitorCaptureDevicesInternal,
-                 BrowserMainLoop::GetInstance()->media_stream_manager()));
-}
-
-}  // namespace content