Improve validation of external extension ids.

chrome/browser/extensions/external_extension_provider_interface.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_PROVIDER_INTERFACE_H_
 #define CHROME_BROWSER_EXTENSIONS_EXTERNAL_EXTENSION_PROVIDER_INTERFACE_H_
 #pragma once
 
 #include <vector>
 
 #include "base/linked_ptr.h"
 #include "chrome/common/extensions/extension.h"
 
 class FilePath;
 class Version;
 
 // This class is an abstract class for implementing external extensions
 // providers.
 class ExternalExtensionProviderInterface {
  public:
   // ExternalExtensionProvider uses this interface to communicate back to the
   // caller what extensions are registered, and which |id|, |version| and |path|
   // they have. See also VisitRegisteredExtension below. Ownership of |version|
-  // is not transferred to the visitor.
+  // is not transferred to the visitor.  Callers of the methods below must
+  // ensure that |id| is a valid extension id (use Extension::IdIsValid(id)).
   class VisitorInterface {
    public:
-     virtual void OnExternalExtensionFileFound(
-         const std::string& id,
-         const Version* version,
-         const FilePath& path,
-         Extension::Location location) = 0;
+    virtual void OnExternalExtensionFileFound(
+        const std::string& id,
+        const Version* version,
+        const FilePath& path,
+        Extension::Location location) = 0;
 
-     virtual void OnExternalExtensionUpdateUrlFound(
-         const std::string& id,
-         const GURL& update_url,
-         Extension::Location location) = 0;
+    virtual void OnExternalExtensionUpdateUrlFound(
+        const std::string& id,
+        const GURL& update_url,
+        Extension::Location location) = 0;
 
      // Called after all the external extensions have been reported through
      // the above two methods.
-     virtual void OnExternalProviderReady() = 0;
+    virtual void OnExternalProviderReady() = 0;
 
    protected:
-     virtual ~VisitorInterface() {}
+    virtual ~VisitorInterface() {}
   };
 
   virtual ~ExternalExtensionProviderInterface() {}
 
   // The visitor (ExtensionsService) calls this function before it goes away.
   virtual void ServiceShutdown() = 0;
 
   // Enumerate registered extensions, calling
   // OnExternalExtension(File|UpdateUrl)Found on the |visitor| object for each
   // registered extension found.
@@ skipping 12 matching lines @@
 
   // Determines if this provider had loaded the list of external extensions
   // from its source.
   virtual bool IsReady() = 0;
 };
 
 typedef std::vector<linked_ptr<ExternalExtensionProviderInterface> >
     ProviderCollection;
 
 #endif  // CHROME_BROWSER_EXTENSIONS_EXTERNAL_EXTENSION_PROVIDER_INTERFACE_H_