reapply r70628. It was wrongly blamed for breaking Linux valgrind bots.

net/http/http_cache.h

Index: net/http/http_cache.h
diff --git a/net/http/http_cache.h b/net/http/http_cache.h
index 8ff64429737566ee5d28824be4ccbd1ebc64abc0..0641ca4dcf9e1d93661583b2300cedc5e5c9948c 100644
--- a/net/http/http_cache.h
+++ b/net/http/http_cache.h
@@ -87,7 +87,8 @@ class HttpCache : public HttpTransactionFactory,
     // notification arrives.
     // The implementation must not access the factory object after invoking the
     // |callback| because the object can be deleted from within the callback.
-    virtual int CreateBackend(disk_cache::Backend** backend,
+    virtual int CreateBackend(NetLog* net_log,
+                              disk_cache::Backend** backend,
                               CompletionCallback* callback) = 0;
   };
 
@@ -105,7 +106,8 @@ class HttpCache : public HttpTransactionFactory,
     static BackendFactory* InMemory(int max_bytes);
 
     // BackendFactory implementation.
-    virtual int CreateBackend(disk_cache::Backend** backend,
+    virtual int CreateBackend(NetLog* net_log,
+                              disk_cache::Backend** backend,
                               CompletionCallback* callback);
 
    private:
@@ -140,6 +142,7 @@ class HttpCache : public HttpTransactionFactory,
   // by the HttpCache and will be destroyed using |delete| when the HttpCache is
   // destroyed.
   HttpCache(HttpTransactionFactory* network_layer,
+            NetLog* net_log,
             BackendFactory* backend_factory);
 
   HttpTransactionFactory* network_layer() { return network_layer_.get(); }
@@ -215,7 +218,7 @@ class HttpCache : public HttpTransactionFactory,
     bool               will_process_pending_queue;
     bool               doomed;
 
-    explicit ActiveEntry(disk_cache::Entry*);
+    explicit ActiveEntry(disk_cache::Entry* entry);
     ~ActiveEntry();
   };
 
@@ -344,6 +347,8 @@ class HttpCache : public HttpTransactionFactory,
 
   // Variables ----------------------------------------------------------------
 
+  NetLog* net_log_;
+
   // Used when lazily constructing the disk_cache_.
   scoped_ptr<BackendFactory> backend_factory_;
   bool building_backend_;