Adaptive delay between successive component updates.

components/update_client/crx_update_item.h

Index: components/update_client/crx_update_item.h
diff --git a/components/update_client/crx_update_item.h b/components/update_client/crx_update_item.h
index b7c1ba1f157e9e3aa5a0adb6f36ada6e79ea54d6..84ee7676bf75f2af51853337db54407a5cabc7b8 100644
--- a/components/update_client/crx_update_item.h
+++ b/components/update_client/crx_update_item.h
@@ -79,8 +79,12 @@ struct CrxUpdateItem {
   std::string id;
   CrxComponent component;
 
+  // Time when an update check for this CRX has happened.
   base::Time last_check;
 
+  // Time when the update of this CRX has begun.
+  base::TimeTicks update_begin;
+
   // A component can be made available for download from several urls.
   std::vector<GURL> crx_urls;
   std::vector<GURL> crx_diffurls;