Adds NavigationManager util functions to ios/chrome/browser/web/

ios/chrome/browser/web/navigation_manager_util.mm

Index: ios/chrome/browser/web/navigation_manager_util.mm
diff --git a/ios/chrome/browser/web/navigation_manager_util.mm b/ios/chrome/browser/web/navigation_manager_util.mm
new file mode 100644
index 0000000000000000000000000000000000000000..6e1fd30072306d649af9d8b5f1121d12fbd6b39e
--- /dev/null
+++ b/ios/chrome/browser/web/navigation_manager_util.mm
@@ -0,0 +1,25 @@
+// Copyright 2017 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "ios/chrome/browser/web/navigation_manager_util.h"
+
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
+
+web::NavigationItem* GetLastNonRedirectedItem(
+    web::NavigationManager* nav_manager) {
+  if (!nav_manager->GetItemCount())
+    return nullptr;
+  int index = nav_manager->GetCurrentItemIndex();
+  web::NavigationItem* item = nullptr;
+  while (index >= 0) {
+    item = nav_manager->GetItemAtIndex(index);
+    // Skips navigation item if it is for a kind of HTTP Redirect.

[kkhorimoto, 2017/03/17 01:18:01]

"Skips" is a little misleading; I would expect a continue rather than a break
from reading this comment.  Maybe s/Skips/Returns?

[pkl (ping after 24h if needed), 2017/03/17 01:25:08]

It's not just misleading...it's wrong. Thanks for catching this.
I changed the code, but not the comment. Corrected now.

+    if ((item->GetTransitionType() & ui::PAGE_TRANSITION_IS_REDIRECT_MASK) == 0)
+      break;
+    --index;
+  }
+  return item;
+}