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 fcdf2a9fffae5083c0915c1782ead31a482d96a1..8c575400a67e7f28714fe5f4820b87d42fa0e2b4 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_;
   }
 
+  std::string GetMediaDeviceIDSalt() const;
+
   net::TransportSecurityState* transport_security_state() const {
     return transport_security_state_.get();
   }
@@ -464,6 +467,8 @@ class ProfileIOData {
 
   mutable StringListPrefMember one_click_signin_rejected_email_list_;
 
+  mutable scoped_ptr<MediaDeviceIDSalt> media_device_id_salt_;
+
   // Member variables which are pointed to by the various context objects.
   mutable BooleanPrefMember enable_referrers_;
   mutable BooleanPrefMember enable_do_not_track_;