Install CRX updates one at a time.

chrome/browser/extensions/extension_service.cc

Index: chrome/browser/extensions/extension_service.cc
diff --git a/chrome/browser/extensions/extension_service.cc b/chrome/browser/extensions/extension_service.cc
index a409420dfbb39c47d0085be060892b98f24856c5..308125f13ed5d9a86f6979ef5d754212ba01cd56 100644
--- a/chrome/browser/extensions/extension_service.cc
+++ b/chrome/browser/extensions/extension_service.cc
@@ -600,9 +600,11 @@ void ExtensionService::Init() {
   GarbageCollectExtensions();
 }
 
-void ExtensionService::UpdateExtension(const std::string& id,
-                                       const FilePath& extension_path,
-                                       const GURL& download_url) {
+bool ExtensionService::UpdateExtension(
+    const std::string& id,
+    const FilePath& extension_path,
+    const GURL& download_url,
+    Source<CrxInstaller>* out_install_notification_source) {
   CHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
 
   PendingExtensionInfo pending_extension_info;
@@ -621,7 +623,8 @@ void ExtensionService::UpdateExtension(const std::string& id,
             NewRunnableFunction(
                 extension_file_util::DeleteFile, extension_path, false)))
       NOTREACHED();
-    return;
+
+    return false;
   }
 
   // We want a silent install only for non-pending extensions and
@@ -640,6 +643,11 @@ void ExtensionService::UpdateExtension(const std::string& id,
   installer->set_original_url(download_url);
   installer->set_install_cause(extension_misc::INSTALL_CAUSE_UPDATE);
   installer->InstallCrx(extension_path);
+
+  if (out_install_notification_source)
+    *out_install_notification_source = Source<CrxInstaller>(installer);
+
+  return true;
 }
 
 void ExtensionService::ReloadExtension(const std::string& extension_id) {