SupportsUserData is not thread safe

content/browser/resource_context_impl.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "content/browser/resource_context_impl.h"
 
 #include "base/logging.h"
 #include "content/browser/appcache/chrome_appcache_service.h"
 #include "content/browser/fileapi/browser_file_system_helper.h"
 #include "content/browser/fileapi/chrome_blob_storage_context.h"
@@ skipping 264 matching lines @@
       kBlobStorageContextKeyName,
       new UserDataAdapter<ChromeBlobStorageContext>(
           ChromeBlobStorageContext::GetFor(browser_context)));
 
   // This object is owned by the BrowserContext and not ResourceContext, so
   // store a non-owning pointer here.
   resource_context->SetUserData(
       kHostZoomMapKeyName,
       new NonOwningZoomData(
           HostZoomMap::GetForBrowserContext(browser_context)));
+  resource_context->DetachUserDataThread();
 
   // Add content's URLRequestContext's hooks.
   // Check first to avoid memory leak in unittests.
   // TODO(creis): Do equivalent initializations for isolated app and isolated
   // media request contexts.
   if (BrowserThread::IsMessageLoopValid(BrowserThread::IO)) {
     // TODO(ajwong): Move this whole block into
     // StoragePartitionImplMap::PostCreateInitialization after we're certain
     // this is safe to happen before InitializeResourceContext, and after we've
     // found the right URLRequestContext for a storage partition.  Otherwise,
@@ skipping 19 matching lines @@
             make_scoped_refptr(browser_context->GetMediaRequestContext()),
             BrowserContext::GetAppCacheService(browser_context),
             make_scoped_refptr(
                 BrowserContext::GetFileSystemContext(browser_context)),
             make_scoped_refptr(
                 ChromeBlobStorageContext::GetFor(browser_context))));
   }
 }
 
 }  // namespace content