Install CRX updates one at a time.

chrome/browser/extensions/test_extension_service.h

Index: chrome/browser/extensions/test_extension_service.h
diff --git a/chrome/browser/extensions/test_extension_service.h b/chrome/browser/extensions/test_extension_service.h
index 5977c5c6b3f2a9f264e830e206e0ce7a6abc8133..3ef612ef338b34e36c7040c45149ae9ecd9f480f 100644
--- a/chrome/browser/extensions/test_extension_service.h
+++ b/chrome/browser/extensions/test_extension_service.h
@@ -11,6 +11,8 @@
 
 #include "chrome/browser/extensions/extension_service.h"
 
+class CrxInstaller;
+
 // Implemention of ExtensionServiceInterface with default
 // implementations for methods that add failures.  You should subclass
 // this and override the methods you care about.
@@ -21,9 +23,16 @@ class TestExtensionService : public ExtensionServiceInterface {
   // ExtensionServiceInterface implementation.
   virtual const ExtensionList* extensions() const OVERRIDE;
   virtual PendingExtensionManager* pending_extension_manager() OVERRIDE;
-  virtual void UpdateExtension(const std::string& id,
-                               const FilePath& path,
-                               const GURL& download_url) OVERRIDE;
+
+  // Install an update.  Return true if the install can be started.

[Matt Perry, 2011/05/31 21:34:25]

remove the comment for derived classes

[Sam Kerner (Chrome), 2011/05/31 23:16:15]

Done.

+  // CRX installs send event NotificationType::CRX_INSTALLER_DONE when
+  // complete.  Set *out_install_notification_source to the source of
+  // that notification for this update.
+  virtual bool UpdateExtension(
+      const std::string& id,
+      const FilePath& path,
+      const GURL& download_url,
+      Source<CrxInstaller>* out_install_notification_source) OVERRIDE;
   virtual const Extension* GetExtensionById(
       const std::string& id, bool include_disabled) const OVERRIDE;
   virtual const Extension* GetInstalledExtension(