Revert of Make default media device ID salts random by default

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 5c4d65b1023f40e7bba584af83843c3758522b34..ba4ecf650be61d8126b7f6174e5fe9b0e73a22c7 100644
--- a/chrome/browser/profiles/profile_io_data.cc
+++ b/chrome/browser/profiles/profile_io_data.cc
@@ -499,8 +499,7 @@
     signin_allowed_.MoveToThread(io_task_runner);
   }
 
-  if (!IsOffTheRecord())
-    media_device_id_salt_ = new MediaDeviceIDSalt(pref_service);
+  media_device_id_salt_ = new MediaDeviceIDSalt(pref_service, IsOffTheRecord());
 
   network_prediction_options_.Init(prefs::kNetworkPredictionOptions,
                                    pref_service);
@@ -866,9 +865,8 @@
   return host_content_settings_map_.get();
 }
 
-std::string ProfileIOData::GetMediaDeviceIDSalt() const {
-  DCHECK(media_device_id_salt_);
-  return media_device_id_salt_->GetSalt();
+ResourceContext::SaltCallback ProfileIOData::GetMediaDeviceIDSalt() const {
+  return base::Bind(&MediaDeviceIDSalt::GetSalt, media_device_id_salt_);
 }
 
 bool ProfileIOData::IsOffTheRecord() const {
@@ -1005,11 +1003,9 @@
 #endif
 }
 
-std::string ProfileIOData::ResourceContext::GetMediaDeviceIDSalt() {
-  if (io_data_->HasMediaDeviceIDSalt())
-    return io_data_->GetMediaDeviceIDSalt();
-
-  return content::ResourceContext::GetMediaDeviceIDSalt();
+ResourceContext::SaltCallback
+ProfileIOData::ResourceContext::GetMediaDeviceIDSalt() {
+  return io_data_->GetMediaDeviceIDSalt();
 }
 
 void ProfileIOData::Init(