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

content/browser/appcache/appcache_backend_impl.cc

Index: content/browser/appcache/appcache_backend_impl.cc
diff --git a/content/browser/appcache/appcache_backend_impl.cc b/content/browser/appcache/appcache_backend_impl.cc
index e055f1a1de8465ee7ec45eb386593bb8be1ecd55..01eed000ef0a21f77d6b4d692f66d918565d3f0a 100644
--- a/content/browser/appcache/appcache_backend_impl.cc
+++ b/content/browser/appcache/appcache_backend_impl.cc
@@ -68,32 +68,29 @@ bool AppCacheBackendImpl::SelectCache(
     const int64 cache_document_was_loaded_from,
     const GURL& manifest_url) {
   AppCacheHost* host = GetHost(host_id);
-  if (!host || host->was_select_cache_called())
+  if (!host)
     return false;
 
-  host->SelectCache(document_url, cache_document_was_loaded_from,
+  return host->SelectCache(document_url, cache_document_was_loaded_from,
                     manifest_url);
-  return true;
 }
 
 bool AppCacheBackendImpl::SelectCacheForWorker(
     int host_id, int parent_process_id, int parent_host_id) {
   AppCacheHost* host = GetHost(host_id);
-  if (!host || host->was_select_cache_called())
+  if (!host)
     return false;
 
-  host->SelectCacheForWorker(parent_process_id, parent_host_id);
-  return true;
+  return host->SelectCacheForWorker(parent_process_id, parent_host_id);
 }
 
 bool AppCacheBackendImpl::SelectCacheForSharedWorker(
     int host_id, int64 appcache_id) {
   AppCacheHost* host = GetHost(host_id);
-  if (!host || host->was_select_cache_called())
+  if (!host)
     return false;
 
-  host->SelectCacheForSharedWorker(appcache_id);
-  return true;
+  return host->SelectCacheForSharedWorker(appcache_id);
 }
 
 bool AppCacheBackendImpl::MarkAsForeignEntry(
@@ -104,8 +101,7 @@ bool AppCacheBackendImpl::MarkAsForeignEntry(
   if (!host)
     return false;
 
-  host->MarkAsForeignEntry(document_url, cache_document_was_loaded_from);
-  return true;
+  return host->MarkAsForeignEntry(document_url, cache_document_was_loaded_from);
 }
 
 bool AppCacheBackendImpl::GetStatusWithCallback(