Ensure we don't crash if user navigates back from NTP to Chrome sign-in page before it has fully lo…

chrome/browser/safe_browsing/safe_browsing_blocking_page.cc

 // Copyright (c) 2012 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.
 //
 // Implementation of the SafeBrowsingBlockingPage class.
 
 #include "chrome/browser/safe_browsing/safe_browsing_blocking_page.h"
 
 #include <string>
 
@@ skipping 464 matching lines @@
   // We don't remove the navigation entry if the tab is being destroyed as this
   // would trigger a navigation that would cause trouble as the render view host
   // for the tab has by then already been destroyed.  We also don't delete the
   // current entry if it has been committed again, which is possible on a page
   // that had a subresource warning.
   int last_committed_index =
       web_contents_->GetController().GetLastCommittedEntryIndex();
   if (navigation_entry_index_to_remove_ != -1 &&
       navigation_entry_index_to_remove_ != last_committed_index &&
       !web_contents_->IsBeingDestroyed()) {
-    web_contents_->GetController().RemoveEntryAtIndex(
-        navigation_entry_index_to_remove_);
+    CHECK(web_contents_->GetController().RemoveEntryAtIndex(
+        navigation_entry_index_to_remove_));
     navigation_entry_index_to_remove_ = -1;
   }
 }
 
 void SafeBrowsingBlockingPage::RecordUserAction(BlockingPageEvent event) {
   // This enum is used for a histogram.  Don't reorder, delete, or insert
   // elements.  New elements should be added before MAX_ACTION only.
   enum {
     MALWARE_SHOW = 0,
     MALWARE_DONT_PROCEED,
@@ skipping 626 matching lines @@
   strings->SetString("details", std::string());
   strings->SetString("confirm_text", std::string());
   strings->SetString(kBoxChecked, std::string());
   strings->SetString(
       "report_error",
       l10n_util::GetStringUTF16(IDS_SAFE_BROWSING_PHISHING_V2_REPORT_ERROR));
   strings->SetBoolean(kDisplayCheckBox, false);
   strings->SetString("learnMore",
       l10n_util::GetStringUTF16(IDS_SAFE_BROWSING_MALWARE_V2_LEARN_MORE));
 }