Prevent a possible crash on omnibox navigation.

chrome/browser/ui/omnibox/omnibox_navigation_observer.cc

Index: chrome/browser/ui/omnibox/omnibox_navigation_observer.cc
diff --git a/chrome/browser/ui/omnibox/omnibox_navigation_observer.cc b/chrome/browser/ui/omnibox/omnibox_navigation_observer.cc
index 040dbdefa2cfcd57bace95ae91c9f25a2bc92c59..b8afea78c4aa52205699a0c5acf358f6c5a4e990 100644
--- a/chrome/browser/ui/omnibox/omnibox_navigation_observer.cc
+++ b/chrome/browser/ui/omnibox/omnibox_navigation_observer.cc
@@ -86,15 +86,27 @@ void OmniboxNavigationObserver::Observe(
     const content::NotificationSource& source,
     const content::NotificationDetails& details) {
   DCHECK_EQ(content::NOTIFICATION_NAV_ENTRY_PENDING, type);
-  registrar_.Remove(this, content::NOTIFICATION_NAV_ENTRY_PENDING,
-                    content::NotificationService::AllSources());
+
+  // It's possible for an attempted omnibox navigation to cause the extensions
+  // system to synchronously navigate an extension background page.  Not only is
+  // this navigation not the one we want to observe, the associated WebContents
+  // is invisible and has no InfoBarService, so trying to show an infobar in it
+  // later will crash.  Just ignore this navigation and keep listening.
   content::NavigationController* controller =
       content::Source<content::NavigationController>(source).ptr();
+  content::WebContents* web_contents = controller->GetWebContents();
+  if (!InfoBarService::FromWebContents(web_contents))

[Vitaly Buka (NO REVIEWS), 2015/01/22 21:59:09]

Using InfoBarservice for unwanted web-contents looks confusing.
It would be nicer to have more direct check.

Maybe opposite?

if (match_.destination_url != ...) {
...
}
and CHECK for InfoBarService...

[Peter Kasting, 2015/01/22 22:02:26]

There's no theoretical reason why an extension background page couldn't load the
same page the user is trying to load, so there's a chance (although it seems
very unlikely) that doing things that way would break.

+    return;
+
+  CHECK_EQ(match_.destination_url,
+           content::Details<content::NavigationEntry>(details)->GetURL());
+  registrar_.Remove(this, content::NOTIFICATION_NAV_ENTRY_PENDING,
+                    content::NotificationService::AllSources());
   if (fetcher_) {
     fetcher_->SetRequestContext(
         controller->GetBrowserContext()->GetRequestContext());
   }
-  WebContentsObserver::Observe(controller->GetWebContents());
+  WebContentsObserver::Observe(web_contents);
   // DidStartNavigationToPendingEntry() will be called for this load as well.
 }