Created SerializedUserDataManager.

ios/web/web_state/web_state_impl.mm

Index: ios/web/web_state/web_state_impl.mm
diff --git a/ios/web/web_state/web_state_impl.mm b/ios/web/web_state/web_state_impl.mm
index 17e4a547e043d5033101724aa4243cfe295b844e..07e59a926b5085fb9c17ad1f86cbde7fdacc6b13 100644
--- a/ios/web/web_state/web_state_impl.mm
+++ b/ios/web/web_state/web_state_impl.mm
@@ -12,6 +12,7 @@
 #include "ios/web/net/request_group_util.h"
 #include "ios/web/public/browser_state.h"
 #include "ios/web/public/navigation_item.h"
+#include "ios/web/public/serialized_user_data_manager.h"
 #include "ios/web/public/url_util.h"
 #include "ios/web/public/web_client.h"
 #include "ios/web/public/web_state/credential.h"
@@ -107,8 +108,19 @@ void WebStateImpl::SetFacadeDelegate(WebStateFacadeDelegate* facade_delegate) {
 }
 
 scoped_ptr<WebStateImpl> WebStateImpl::CopyForSerialization() const {
-  return scoped_ptr<WebStateImpl>(new WebStateImpl(
+  scoped_ptr<WebStateImpl> copy(new WebStateImpl(
       GetBrowserState(), navigation_manager_->CopyForSerialization()));
+  // Copy the serialized user data and detach the user data thread so the newly
+  // created WebState can be serialized on another thread.
+  WebStateImpl* non_const_this = const_cast<WebStateImpl*>(this);

[Eugene But (OOO till 7-30), 2015/09/24 21:39:25]

This is a violation of API contract. This method promises to be const, but it
changes WebState.

+  SerializedUserDataManager* user_data_manager =
+      SerializedUserDataManager::FromWebState(non_const_this);
+  SerializedUserDataManager* copy_user_data_manager =
+      SerializedUserDataManager::FromWebState(copy.get());
+  copy_user_data_manager->AddValuesFromDictionary(
+      user_data_manager->GetSerializationDictionary());
+  copy->DetachUserDataThread();
+  return copy.Pass();
 }
 
 void WebStateImpl::OnUrlHashChanged() {