Merge 141090 - Add some NULL-checks for ExtensionHost::extension to fix a crash bug.

chrome/browser/extensions/extension_event_router.cc

Index: chrome/browser/extensions/extension_event_router.cc
===================================================================
--- chrome/browser/extensions/extension_event_router.cc	(revision 141761)
+++ chrome/browser/extensions/extension_event_router.cc	(working copy)
@@ -425,6 +425,9 @@
   // The event ACK is routed to the background host, so this should never be
   // NULL.
   CHECK(host);
+  if (!host->extension())
+    return;
+
   CHECK(host->extension()->has_lazy_background_page());
   pm->DecrementLazyKeepaliveCount(host->extension());
 }