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

chrome/browser/profiles/profile_io_data.h

Index: chrome/browser/profiles/profile_io_data.h
diff --git a/chrome/browser/profiles/profile_io_data.h b/chrome/browser/profiles/profile_io_data.h
index 724a728b1493bb5ba811b9e14eb83c9f81ebb372..76a766920c531fe9822b992baa04792f1d7f91ae 100644
--- a/chrome/browser/profiles/profile_io_data.h
+++ b/chrome/browser/profiles/profile_io_data.h
@@ -33,6 +33,7 @@ class DesktopNotificationService;
 class ExtensionInfoMap;
 class HostContentSettingsMap;
 class ManagedModeURLFilter;
+class MediaDeviceIDSalt;
 class Profile;
 class ProtocolHandlerRegistry;
 class SigninNamesOnIOThread;
@@ -173,6 +174,8 @@ class ProfileIOData {
     return &signin_allowed_;
   }
 
+  const std::string& media_device_id_salt() const;
+
   net::TransportSecurityState* transport_security_state() const {
     return transport_security_state_.get();
   }
@@ -529,6 +532,8 @@ class ProfileIOData {
 
   mutable chrome_browser_net::LoadTimeStats* load_time_stats_;
 
+  mutable scoped_ptr<MediaDeviceIDSalt> media_device_id_salt_;
+
 #if defined(ENABLE_MANAGED_USERS)
   mutable scoped_refptr<const ManagedModeURLFilter> managed_mode_url_filter_;
 #endif