Make quota requests from background pages not crash

chrome/browser/chrome_quota_permission_context.cc

Index: chrome/browser/chrome_quota_permission_context.cc
diff --git a/chrome/browser/chrome_quota_permission_context.cc b/chrome/browser/chrome_quota_permission_context.cc
index 8c7c6d5ad081be538a4934e2c22e7c885d4ee172..bb583c605c76d1a5a7ce7ad6c96f6033ca837518 100644
--- a/chrome/browser/chrome_quota_permission_context.cc
+++ b/chrome/browser/chrome_quota_permission_context.cc
@@ -138,7 +138,8 @@ void ChromeQuotaPermissionContext::RequestQuotaPermission(
   }
 
   TabContents* tab_contents = TabContents::FromWebContents(web_contents);
-  InfoBarTabHelper* infobar_helper = tab_contents->infobar_tab_helper();
+  InfoBarTabHelper* infobar_helper =
+      tab_contents ? tab_contents->infobar_tab_helper() : NULL;
   if (!infobar_helper) {
     // The tab has no infobar helper.
     LOG(WARNING) << "Attempt to request quota from a background page: "