ExtensionService: Delay non-critical IO until after startup has finished.

chrome/browser/extensions/extension_service.h

Index: chrome/browser/extensions/extension_service.h
diff --git a/chrome/browser/extensions/extension_service.h b/chrome/browser/extensions/extension_service.h
index 7b025ad690cb47b3303dd5be45e6641294ec5eb8..9d52cb9ac1e414c694d03733f20486894434f521 100644
--- a/chrome/browser/extensions/extension_service.h
+++ b/chrome/browser/extensions/extension_service.h
@@ -380,6 +380,13 @@ class ExtensionService
   // Check for updates (or potentially new extensions from external providers)
   void CheckForExternalUpdates();
 
+  // For testing: CheckForExternalUpdates() is idempotent.  Reset the flag
+  // that causes the function to perform an early return after it's first
+  // invocation.
+  void ResetExternalUpdateCheckGuardForTests() {
+    external_update_check_has_run_ = false;
+  }
+
   // Unload the specified extension.
   virtual void UnloadExtension(
       const std::string& extension_id,
@@ -894,6 +901,9 @@ class ExtensionService
   // has fired.
   bool ready_;
 
+  // Have we done an external update check yet?
+  bool external_update_check_has_run_;
+
   // Our extension updater, if updates are turned on.
   scoped_ptr<extensions::ExtensionUpdater> updater_;