Code:  bool AppCacheBackendImpl::SelectCacheForSharedWorker(
     int host_id, int64 appcache_id) {
   AppCacheHost* host = GetHost(host_id);
  if (!host || host->was_select_cache_called())
     return false;
 
  host->SelectCacheForSharedWorker(appcache_id);
  return true;
 }

Vulnerability Type: DoS 
CWE ID: 
Summary: Use-after-free vulnerability in the AppCache implementation in Google Chrome before 47.0.2526.73 allows remote attackers with renderer access to cause a denial of service or possibly have unspecified other impact by leveraging incorrect AppCacheUpdateJob behavior associated with duplicate cache selection.
Commit Message: Fix possible map::end() dereference in AppCacheUpdateJob triggered by a compromised renderer.

BUG=551044

Review URL: https://codereview.chromium.org/1418783005

Cr-Commit-Position: refs/heads/master@{#358815}