Fall back to local page if online NTP fails to load.

chrome/browser/ui/search/instant_page.cc

 // Copyright 2013 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 "chrome/browser/ui/search/instant_page.h"
 
 #include "base/utf_string_conversions.h"
 #include "chrome/common/render_messages.h"
 #include "chrome/common/url_constants.h"
+#include "content/public/browser/navigation_details.h"
 #include "content/public/browser/web_contents.h"
+#include "content/public/common/frame_navigate_params.h"
 #include "ui/base/resource/resource_bundle.h"
 #include "ui/gfx/font.h"
 
 InstantPage::Delegate::~Delegate() {
 }
 
 InstantPage::~InstantPage() {
 }
 
 bool InstantPage::IsLocal() const {
@@ skipping 164 matching lines @@
 void InstantPage::DidCommitProvisionalLoadForFrame(
     int64 /* frame_id */,
     bool is_main_frame,
     const GURL& url,
     content::PageTransition /* transition_type */,
     content::RenderViewHost* /* render_view_host */) {
   if (is_main_frame && ShouldProcessAboutToNavigateMainFrame())
     delegate_->InstantPageAboutToNavigateMainFrame(contents(), url);
 }
 
+void InstantPage::DidFailProvisionalLoad(
+    int64 frame_id,

[samarth, 2013/05/01 06:26:47]

nit: comment out the parameter names that you won't use

[David Black, 2013/05/02 00:49:45]

Done.

+    bool is_main_frame,
+    const GURL& validated_url,
+    int error_code,
+    const string16& error_description,
+    content::RenderViewHost* render_view_host) {
+  delegate_->InstantPageLoadFailed(contents());
+}
+
 void InstantPage::OnSetSuggestions(
     int page_id,
     const std::vector<InstantSuggestion>& suggestions) {
   if (contents()->IsActiveEntry(page_id)) {
     OnInstantSupportDetermined(page_id, true);
     if (ShouldProcessSetSuggestions())
       delegate_->SetSuggestions(contents(), suggestions);
   }
 }
 
@@ skipping 45 matching lines @@
   delegate_->DeleteMostVisitedItem(restricted_id);
 }
 
 void InstantPage::OnUndoMostVisitedDeletion(InstantRestrictedID restricted_id) {
   delegate_->UndoMostVisitedDeletion(restricted_id);
 }
 
 void InstantPage::OnUndoAllMostVisitedDeletions() {
   delegate_->UndoAllMostVisitedDeletions();
 }
+
+void InstantPage::DidNavigateMainFrame(
+      const content::LoadCommittedDetails& details,
+      const content::FrameNavigateParams& params) {

[samarth, 2013/05/01 06:26:47]

Likewise, here

[David Black, 2013/05/02 00:49:45]

Done.

+  // A 204 can be sent by the search provider as a lightweight signal
+  // to fall back to the local page, and we obviously want to fall back
+  // if we get any response code that indicates an error.
+  if (details.http_status_code == 204 || details.http_status_code >= 400)
+    delegate_->InstantPageLoadFailed(contents());
+}