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

chrome/browser/profiles/profile_io_data.cc

Index: chrome/browser/profiles/profile_io_data.cc
diff --git a/chrome/browser/profiles/profile_io_data.cc b/chrome/browser/profiles/profile_io_data.cc
index ff66f912d7aed54c85d0a58c95ec2ff1d91e956b..e809e8607c7e3c5718a9a32164804478ddcdf2d6 100644
--- a/chrome/browser/profiles/profile_io_data.cc
+++ b/chrome/browser/profiles/profile_io_data.cc
@@ -35,6 +35,7 @@
 #include "chrome/browser/extensions/extension_resource_protocols.h"
 #include "chrome/browser/extensions/extension_system.h"
 #include "chrome/browser/io_thread.h"
+#include "chrome/browser/media/media_device_id_salt.h"
 #include "chrome/browser/net/about_protocol_handler.h"
 #include "chrome/browser/net/chrome_cookie_notification_details.h"
 #include "chrome/browser/net/chrome_fraudulent_certificate_reporter.h"
@@ -315,6 +316,7 @@ void ProfileIOData::InitializeOnUIThread(Profile* profile) {
   printing_enabled_.Init(prefs::kPrintingEnabled, pref_service);
   printing_enabled_.MoveToThread(io_message_loop_proxy);
 #endif
+
   chrome_http_user_agent_settings_.reset(
       new ChromeHttpUserAgentSettings(pref_service));
 
@@ -346,6 +348,9 @@ void ProfileIOData::InitializeOnUIThread(Profile* profile) {
     signin_allowed_.MoveToThread(io_message_loop_proxy);
   }
 
+  media_device_id_salt_.reset(new MediaDeviceIDSalt(pref_service,
+                                                    is_incognito()));
+
   // The URLBlacklistManager has to be created on the UI thread to register
   // observers of |pref_service|, and it also has to clean up on
   // ShutdownOnUIThread to release these observers on the right thread.
@@ -645,6 +650,10 @@ DesktopNotificationService* ProfileIOData::GetNotificationService() const {
 }
 #endif
 
+std::string ProfileIOData::GetMediaDeviceIDSalt() const {
+  return media_device_id_salt_->GetSalt();
+}
+
 void ProfileIOData::InitializeMetricsEnabledStateOnUIThread() {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
 #if defined(OS_CHROMEOS)
@@ -945,6 +954,7 @@ void ProfileIOData::ShutdownOnUIThread() {
   printing_enabled_.Destroy();
   sync_disabled_.Destroy();
   signin_allowed_.Destroy();
+  media_device_id_salt_.reset(NULL);
   session_startup_pref_.Destroy();
 #if defined(ENABLE_CONFIGURATION_POLICY)
   if (url_blacklist_manager_)