Enable forced extension updates on NaCl arch mismatch.

chrome/browser/extensions/updater/extension_downloader_delegate.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_UPDATER_EXTENSION_DOWNLOADER_DELEGATE_H_
 #define CHROME_BROWSER_EXTENSIONS_UPDATER_EXTENSION_DOWNLOADER_DELEGATE_H_
 
 #include <set>
 #include <string>
 
@@ skipping 93 matching lines @@
   virtual std::string GetUpdateUrlData(const std::string& id);
 
   // Invoked to determine whether extension |id| is currently
   // pending installation.
   virtual bool IsExtensionPending(const std::string& id) = 0;
 
   // Invoked to get the current version of extension |id|. Returns false if
   // that extension is not installed.
   virtual bool GetExtensionExistingVersion(const std::string& id,
                                            std::string* version) = 0;
+
+  // Determines if a given extension should be forced to update and (if so)
+  // what the source of this forcing is (i.e. what string will be passed
+  // in |installsource| as part of the update query parameters).
+  virtual bool ShouldForceUpdate(const std::string& id,
+                                 std::string* source) = 0;
 };
 
 }  // namespace extensions
 
 #endif  // CHROME_BROWSER_EXTENSIONS_UPDATER_EXTENSION_DOWNLOADER_DELEGATE_H_