Enable forced extension updates on NaCl arch mismatch.

chrome/browser/extensions/updater/extension_downloader_delegate.h

Index: chrome/browser/extensions/updater/extension_downloader_delegate.h
diff --git a/chrome/browser/extensions/updater/extension_downloader_delegate.h b/chrome/browser/extensions/updater/extension_downloader_delegate.h
index a9914c79fcedc410c73e03b2ac4b426158f53046..973adb78c39286700d4a07173a7e339d7981cf03 100644
--- a/chrome/browser/extensions/updater/extension_downloader_delegate.h
+++ b/chrome/browser/extensions/updater/extension_downloader_delegate.h
@@ -111,6 +111,12 @@ class ExtensionDownloaderDelegate {
   // 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