Fix possible map::end() dereference in AppCacheUpdateJob triggered by a compromised renderer.

content/browser/appcache/appcache_update_job.cc

Index: content/browser/appcache/appcache_update_job.cc
diff --git a/content/browser/appcache/appcache_update_job.cc b/content/browser/appcache/appcache_update_job.cc
index 8720fe78e718bfebcbf506aec28fe15a5691530d..ff065503c4deb7afec59aae1bc2645d02b06d095 100644
--- a/content/browser/appcache/appcache_update_job.cc
+++ b/content/browser/appcache/appcache_update_job.cc
@@ -1105,10 +1105,10 @@ void AppCacheUpdateJob::OnDestructionImminent(AppCacheHost* host) {
   // The host is about to be deleted; remove from our collection.
   PendingMasters::iterator found =
       pending_master_entries_.find(host->pending_master_entry_url());
-  DCHECK(found != pending_master_entries_.end());
+  CHECK(found != pending_master_entries_.end());
   PendingHosts& hosts = found->second;
   PendingHosts::iterator it = std::find(hosts.begin(), hosts.end(), host);
-  DCHECK(it != hosts.end());
+  CHECK(it != hosts.end());
   hosts.erase(it);
 }