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 d820172321a2512480e207eac0ca237f1e3b3e3f..136235d543e9a5b79d2f0ea604ab0137cb29efe8 100644
--- a/chrome/browser/profiles/profile_io_data.h
+++ b/chrome/browser/profiles/profile_io_data.h
@@ -31,6 +31,7 @@ class ChromeNetworkDelegate;
 class CookieSettings;
 class HostContentSettingsMap;
 class ManagedModeURLFilter;
+class MediaDeviceIDSalt;
 class Profile;
 class ProtocolHandlerRegistry;
 class SigninNamesOnIOThread;
@@ -170,6 +171,8 @@ class ProfileIOData {
     return &signin_allowed_;
   }
 
+  std::string GetMediaDeviceIDSalt() const;
+
   net::TransportSecurityState* transport_security_state() const {
     return transport_security_state_.get();
   }
@@ -353,6 +356,7 @@ class ProfileIOData {
     virtual scoped_ptr<net::ClientCertStore> CreateClientCertStore() OVERRIDE;
     virtual bool AllowMicAccess(const GURL& origin) OVERRIDE;
     virtual bool AllowCameraAccess(const GURL& origin) OVERRIDE;
+    virtual std::string GetMediaDeviceIDSalt() OVERRIDE;
 
    private:
     friend class ProfileIOData;
@@ -453,6 +457,8 @@ 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_;