Fix windows registry loader to carry over prefs from file thread correctly

chrome/browser/extensions/external_registry_loader_win.h

 // 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.
 
 #ifndef CHROME_BROWSER_EXTENSIONS_EXTERNAL_REGISTRY_LOADER_WIN_H_
 #define CHROME_BROWSER_EXTENSIONS_EXTERNAL_REGISTRY_LOADER_WIN_H_
 
 #include "base/compiler_specific.h"
 #include "base/macros.h"
 #include "base/win/registry.h"
 #include "chrome/browser/extensions/external_loader.h"
 
 namespace extensions {
 
 class ExternalRegistryLoader : public ExternalLoader {
  public:
   ExternalRegistryLoader();
 
  protected:
   ~ExternalRegistryLoader() override {}  // protected for unit test.
 
   void StartLoading() override;
 
+  // Overridden to mock registry reading in unit tests.
+  virtual std::unique_ptr<base::DictionaryValue> LoadPrefsOnFileThread();
+
  private:
   friend class base::RefCountedThreadSafe<ExternalLoader>;
 
-  std::unique_ptr<base::DictionaryValue> LoadPrefsOnFileThread();
   void LoadOnFileThread();
-  void CompleteLoadAndStartWatchingRegistry();
+  void CompleteLoadAndStartWatchingRegistry(
+      std::unique_ptr<base::DictionaryValue> prefs);
   void UpdatePrefsOnFileThread();
   void OnRegistryKeyChanged(base::win::RegKey* key);
 
   // Whether or not we attempted to observe registry.
   bool attempted_watching_registry_;
 
   base::win::RegKey hklm_key_;
   base::win::RegKey hkcu_key_;
 
   DISALLOW_COPY_AND_ASSIGN(ExternalRegistryLoader);
 };
 
 }  // namespace extensions
 
 #endif  // CHROME_BROWSER_EXTENSIONS_EXTERNAL_REGISTRY_LOADER_WIN_H_