Start the extension event routers for each profile, not just at browser startup.

chrome/browser/profiles/profile_impl.cc

Index: chrome/browser/profiles/profile_impl.cc
diff --git a/chrome/browser/profiles/profile_impl.cc b/chrome/browser/profiles/profile_impl.cc
index aff0315d210c3d6617af7441f81d9fc4da843e84..649a8fa4f888a1dfb35a5c60f8d2dc9c27a56a66 100644
--- a/chrome/browser/profiles/profile_impl.cc
+++ b/chrome/browser/profiles/profile_impl.cc
@@ -484,6 +484,16 @@ void ProfileImpl::InitExtensions(bool extensions_enabled) {
 
   // Make the chrome://extension-icon/ resource available.
   GetChromeURLDataManager()->AddDataSource(new ExtensionIconSource(this));
+
+  // Initialize extension event routers. Note that on Chrome OS, this will
+  // not succeed if the user has not logged in yet, in which case the
+  // event routers are initialized in LoginUtilsImpl::CompleteLogin instead.
+  // The InitEventRouters call used to be in BrowserMain, because when bookmark
+  // import happened on first run, the bookmark bar was not being correctly
+  // initialized (see issue 40144). Now that bookmarks aren't imported and
+  // the event routers need to be initialized for every profile individually,
+  // initialize them with the extension service.
+  extension_service_->InitEventRouters();
 }
 
 void ProfileImpl::RegisterComponentExtensions() {