Allow relative paths to external extension files for some providers, error out for others.

chrome/browser/extensions/external_extension_loader.h

 // Copyright (c) 2011 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_EXTENSION_LOADER_H_
 #define CHROME_BROWSER_EXTENSIONS_EXTERNAL_EXTENSION_LOADER_H_
 #pragma once
 
+#include "base/file_path.h"
 #include "base/ref_counted.h"
 #include "base/scoped_ptr.h"
 
 class DictionaryValue;
 class ExternalExtensionProviderImpl;
 
 // Base class for gathering a list of external extensions. Subclasses
 // implement loading from registry, JSON file, policy.
 // Instances are owned by ExternalExtensionProviderImpl objects.
 // Instances are created on the UI thread and expect public method calls from
@@ skipping 15 matching lines @@
   // Called by the owner before it gets deleted.
   void OwnerShutdown();
 
   // Initiates the possibly asynchronous loading of extension list.
   // It is the responsibility of the caller to ensure that calls to
   // this method do not overlap with each other.
   // Implementations of this method should save the loaded results
   // in prefs_ and then call LoadFinished.
   virtual void StartLoading() = 0;
 
+  // Some external providers allow relative file paths to local CRX files.
+  // Subclasses that want this behavior should override this method to
+  // return the absolute path from which relative paths should be resolved.
+  // By default, return an empty path, which indicates that relative paths
+  // are not allowed.
+  virtual const FilePath GetBaseCrxFilePath();
+
  protected:
   virtual ~ExternalExtensionLoader() {}
 
   // Notifies the provider that the list of extensions has been loaded.
   void LoadFinished();
 
   // Used for passing the list of extensions from the method that loads them
   // to |LoadFinished|. To ensure thread safety, the rules are the following:
   // if this value is written on another thread than the UI, then it should
   // only be written in a task that was posted from |StartLoading|. After that,
   // this task should invoke |LoadFinished| with a PostTask. This scheme of
   // posting tasks will avoid concurrent access and imply the necessary memory
   // barriers.
   scoped_ptr<DictionaryValue> prefs_;
 
  private:
   friend class base::RefCountedThreadSafe<ExternalExtensionLoader>;
 
   ExternalExtensionProviderImpl* owner_;  // weak
 
   // Set to true if loading the extensions is already running. New requests
   // are ignored while this is set true.
   bool running_;
 
   DISALLOW_COPY_AND_ASSIGN(ExternalExtensionLoader);
 };
 
 #endif  // CHROME_BROWSER_EXTENSIONS_EXTERNAL_EXTENSION_LOADER_H_