[TooManyTabs] Add TabNavigationThrottle

chrome/common/chrome_features.cc

Index: chrome/common/chrome_features.cc
diff --git a/chrome/common/chrome_features.cc b/chrome/common/chrome_features.cc
index e5446beb3b4f590435e105f728282e9bb1997654..ced395bfeab0d5b6b10bcdf9fc166472924c488e 100644
--- a/chrome/common/chrome_features.cc
+++ b/chrome/common/chrome_features.cc
@@ -315,6 +315,11 @@ const base::Feature kSimplifiedFullscreenUI{"ViewsSimplifiedFullscreenUI",
 const base::Feature kSiteDetails{"SiteDetails",
                                  base::FEATURE_DISABLED_BY_DEFAULT};
 
+// Enables delaying background tabs' opening process in order to improve
+// foreground tab's user experience.
+const base::Feature kStaggeredBackgroundTabOpen{
+    "StaggeredBackgroundTabOpen", base::FEATURE_DISABLED_BY_DEFAULT};
+
 #if defined(SYZYASAN)
 // Enable the deferred free mechanism in the syzyasan module, which helps the
 // performance by deferring some work on the critical path to a background