Revert of Cleaned up old navigation code that did not use pending navigation item.

ios/chrome/browser/experimental_flags.mm

Index: ios/chrome/browser/experimental_flags.mm
diff --git a/ios/chrome/browser/experimental_flags.mm b/ios/chrome/browser/experimental_flags.mm
index 6d6ef70869e297a6b65e20bbaf55f225a8965129..83cd53180ee5d9b6540beb9046ce15b558451af0 100644
--- a/ios/chrome/browser/experimental_flags.mm
+++ b/ios/chrome/browser/experimental_flags.mm
@@ -41,6 +41,8 @@
     @"HeuristicsForPasswordGeneration";
 NSString* const kMDMIntegrationDisabled = @"MDMIntegrationDisabled";
 NSString* const kOriginServerHost = @"AlternateOriginServerHost";
+NSString* const kPendingIndexNavigationDisabled =
+    @"PendingIndexNavigationDisabled";
 NSString* const kSafariVCSignInDisabled = @"SafariVCSignInDisabled";
 NSString* const kWhatsNewPromoStatus = @"WhatsNewPromoStatus";
 
@@ -199,6 +201,11 @@
                           base::CompareCase::INSENSITIVE_ASCII);
 }
 
+bool IsPendingIndexNavigationEnabled() {
+  return ![[NSUserDefaults standardUserDefaults]
+      boolForKey:kPendingIndexNavigationDisabled];
+}
+
 bool IsPhysicalWebEnabled() {
   base::CommandLine* command_line = base::CommandLine::ForCurrentProcess();
   if (command_line->HasSwitch(switches::kEnableIOSPhysicalWeb)) {