Install CRX updates one at a time.

chrome/browser/extensions/extension_service.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_EXTENSION_SERVICE_H_
 #define CHROME_BROWSER_EXTENSIONS_EXTENSION_SERVICE_H_
 #pragma once
 
 #include <map>
 #include <set>
@@ skipping 46 matching lines @@
 class ExtensionServiceInterface {
  public:
   // A function that returns true if the given extension should be
   // included and false if it should be filtered out.  Identical to
   // PendingExtensionInfo::ShouldAllowInstallPredicate.
   typedef bool (*ExtensionFilter)(const Extension&);
 
   virtual ~ExtensionServiceInterface() {}
   virtual const ExtensionList* extensions() const = 0;
   virtual PendingExtensionManager* pending_extension_manager() = 0;
-  virtual void UpdateExtension(const std::string& id,
-                               const FilePath& path,
-                               const GURL& download_url) = 0;
+
+  // Install an update.  Return true if the install can be started.
+  // Set out_crx_installer to the installer if one was started.
+  virtual bool UpdateExtension(
+      const std::string& id,
+      const FilePath& path,
+      const GURL& download_url,
+      CrxInstaller** out_crx_installer) = 0;
   virtual const Extension* GetExtensionById(const std::string& id,
                                             bool include_disabled) const = 0;
   virtual const Extension* GetInstalledExtension(
       const std::string& id) const = 0;
 
   virtual bool IsExtensionEnabled(const std::string& extension_id) const = 0;
   virtual bool IsExternalExtensionUninstalled(
       const std::string& extension_id) const = 0;
 
   virtual void UpdateExtensionBlacklist(
@@ skipping 175 matching lines @@
 
   // Looks up an extension by ID, regardless of whether it's enabled,
   // disabled, or terminated.
   virtual const Extension* GetInstalledExtension(
       const std::string& id) const OVERRIDE;
 
   // Updates a currently-installed extension with the contents from
   // |extension_path|.
   // TODO(aa): This method can be removed. ExtensionUpdater could use
   // CrxInstaller directly instead.
-  virtual void UpdateExtension(const std::string& id,
-                               const FilePath& extension_path,
-                               const GURL& download_url) OVERRIDE;
+  virtual bool UpdateExtension(
+      const std::string& id,
+      const FilePath& extension_path,
+      const GURL& download_url,
+      CrxInstaller** out_crx_installer) OVERRIDE;
 
   // Reloads the specified extension.
   void ReloadExtension(const std::string& extension_id);
 
   // Uninstalls the specified extension. Callers should only call this method
   // with extensions that exist. |external_uninstall| is a magical parameter
   // that is only used to send information to ExtensionPrefs, which external
   // callers should never set to true.
   // TODO(aa): Remove |external_uninstall| -- this information should be passed
   // to ExtensionPrefs some other way.
@@ skipping 418 matching lines @@
   NaClModuleInfoList nacl_module_list_;
 
   FRIEND_TEST_ALL_PREFIXES(ExtensionServiceTest,
                            InstallAppsWithUnlimtedStorage);
   FRIEND_TEST_ALL_PREFIXES(ExtensionServiceTest,
                            InstallAppsAndCheckStorageProtection);
   DISALLOW_COPY_AND_ASSIGN(ExtensionService);
 };
 
 #endif  // CHROME_BROWSER_EXTENSIONS_EXTENSION_SERVICE_H_