Delete PNaCl translation cache backend object when no longer needed

chrome/browser/nacl_host/pnacl_host.h

Index: chrome/browser/nacl_host/pnacl_host.h
diff --git a/chrome/browser/nacl_host/pnacl_host.h b/chrome/browser/nacl_host/pnacl_host.h
index 91553f498492e52d2f39213b35544edfd613604e..782499fb0d675077703ae01dd8108beda7336eca 100644
--- a/chrome/browser/nacl_host/pnacl_host.h
+++ b/chrome/browser/nacl_host/pnacl_host.h
@@ -157,8 +157,13 @@ class PnaclHost {
                               scoped_refptr<net::DrainableIOBuffer> buffer);
   void OnBufferCopiedToTempFile(const TranslationID& id, int file_error);
 
-  static void OnEntriesDoomed(const base::Closure& callback, int net_error);
+  void OnEntriesDoomed(const base::Closure& callback, int net_error);
 
+  void DeInitIfSafe();
+
+  // Operations which are pending with the cache backend, which we should
+  // wait for before destroying it (see comment on DeInitIfSafe).
+  int pending_backend_operations_;
   CacheState cache_state_;
   base::FilePath temp_dir_;
   scoped_ptr<pnacl::PnaclTranslationCache> disk_cache_;