Add DCHECKs to StatefulExternalExtensionProvider

chrome/browser/extensions/stateful_external_extension_provider.h

 // Copyright (c) 2009 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_STATEFUL_EXTERNAL_EXTENSION_PROVIDER_H_
 #define CHROME_BROWSER_EXTENSIONS_STATEFUL_EXTERNAL_EXTENSION_PROVIDER_H_
 #pragma once
 
 #include "chrome/browser/extensions/external_extension_provider.h"
 
 class DictionaryValue;
 class ValueSerializer;
 class Version;
 
 // A specialization of the ExternalExtensionProvider that stores the registered
 // external extensions in a dictionary. This dictionary (|prefs_|) will be used
 // by HasExtension() and GetExtensionDetails() to return information about the
 // stored external extensions. It is the responsibility of specialized
 // subclasses to initialize this internal dictionary.
 // This provider can provide external extensions from two sources: crx files
 // and udpate URLs. The locations that the provider will report for these
 // are specified at the constructor.
+// Instances of this class are expected to be created and destroyed on the UI
+// thread and they are expecting public method calls from the FILE thread.
 class StatefulExternalExtensionProvider : public ExternalExtensionProvider {
  public:
   // Initialize the location for external extensions originating from crx
   // files: |crx_location|, and originating from update URLs:
   // |download_location|. If either of the origins is not supported by this
   // provider, then it should be initialized as Extensions::INVALID.
   StatefulExternalExtensionProvider(
       Extension::Location crx_location,
       Extension::Location download_location);
   virtual ~StatefulExternalExtensionProvider();
 
   // ExternalExtensionProvider implementation:
   virtual void VisitRegisteredExtension(Visitor* visitor) const;
 
   virtual bool HasExtension(const std::string& id) const;
 
   virtual bool GetExtensionDetails(const std::string& id,
                                    Extension::Location* location,
                                    scoped_ptr<Version>* version) const;
  protected:
   // Location for external extensions that are provided by this provider from
   // local crx files.
   const Extension::Location crx_location_;
   // Location for external extensions that are provided by this provider from
   // update URLs.
   const Extension::Location download_location_;
+
+  // Stores the dictionary of external extensions internally. Takes ownership
+  // of |prefs|.
+  void set_prefs(DictionaryValue* prefs);
+
+ private:
   // Dictionary of the external extensions that are provided by this provider.
   scoped_ptr<DictionaryValue> prefs_;
 };
 
 #endif  // CHROME_BROWSER_EXTENSIONS_STATEFUL_EXTERNAL_EXTENSION_PROVIDER_H_