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

chrome/browser/ui/search/instant_page.cc

Index: chrome/browser/ui/search/instant_page.cc
diff --git a/chrome/browser/ui/search/instant_page.cc b/chrome/browser/ui/search/instant_page.cc
index c21c3078477e9fdb8974f9da4181205e97113cf3..e55012e7bebc98f6b0b640c76f3e4627bc34ebd3 100644
--- a/chrome/browser/ui/search/instant_page.cc
+++ b/chrome/browser/ui/search/instant_page.cc
@@ -7,7 +7,9 @@
 #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"
 
@@ -192,6 +194,16 @@ void InstantPage::DidCommitProvisionalLoadForFrame(
     delegate_->InstantPageAboutToNavigateMainFrame(contents(), url);
 }
 
+void InstantPage::DidFailProvisionalLoad(
+    int64 frame_id,
+    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) {
@@ -257,3 +269,10 @@ void InstantPage::OnUndoMostVisitedDeletion(InstantRestrictedID restricted_id) {
 void InstantPage::OnUndoAllMostVisitedDeletions() {
   delegate_->UndoAllMostVisitedDeletions();
 }
+
+void InstantPage::DidNavigateAnyFrame(

[samarth, 2013/04/30 17:10:33]

Why DidNavigateAnyFrame over DidNavigateMainFrame (see
https://code.google.com/p/chromium/codesearch#chromium/src/content/public/bro...
I think this will fire if an iframe on the homepage 404s, which we don't care
about.

[David Black, 2013/04/30 23:09:08]

Ah, I wasn't immediately sure what the difference between the two was so chose
the one that seemed like it would cover more cases.  Switched to MainFrame.

+      const content::LoadCommittedDetails& details,
+      const content::FrameNavigateParams& params) {
+  if (details.http_status_code != 200)

[samarth, 2013/04/30 17:10:33]

There's got to be a helper somewhere in Chrome to distinguish success from
failure using a code. I don't think you want to count 3xx redirects as a failure
for instance.

[David Black, 2013/04/30 23:09:08]

Good point.  Adjusted.  (I wasn't able to find any helper functions in my
cursory search, but >=400 seems like it's just as good.)

+    delegate_->InstantPageLoadFailed(contents());
+}