Make ModelLoader to release URLFeatcher once fetching is done.

chrome/browser/safe_browsing/client_side_model_loader.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/safe_browsing/client_side_model_loader.h"
 
 #include <memory>
 
 #include "base/bind.h"
 #include "base/command_line.h"
@@ skipping 171 matching lines @@
   // If the most recently fetched model had a valid max-age and the model was
   // valid we're scheduling the next model update for after the max-age expired.
   if (!max_age.is_zero() &&
       (status == MODEL_SUCCESS || status == MODEL_NOT_CHANGED)) {
     // We're adding 60s of additional delay to make sure we're past
     // the model's age.
     max_age += base::TimeDelta::FromMinutes(1);
     delay_ms = max_age.InMilliseconds();
   }
 
+  // Reset |fetcher_| as long as it will be re-created on next fetch.

[mattm, 2017/01/30 20:23:13]

Wording is a little confusing, I'd remove the "as long", eg: "Reset |fetcher_|
as it will be re-created on next fetch."

[maksims (do not use this acc), 2017/01/31 05:50:28]

Done.

+  fetcher_.reset();
+
   // Schedule the next model reload.
   ScheduleFetch(delay_ms);
 }
 
 void ModelLoader::ScheduleFetch(int64_t delay_ms) {
   if (base::CommandLine::ForCurrentProcess()->HasSwitch(
-          safe_browsing::switches::kSbDisableAutoUpdate))
+          safe_browsing::switches::kSbDisableAutoUpdate)) {
+    CancelFetcher();

[mattm, 2017/01/30 20:23:13]

This seems unnecessary, can you explain when this would matter?

[maksims (do not use this acc), 2017/01/31 05:50:28]

I thought it would be necessary if fetch had been scheduled before switch became
disabled. But it requires restart of the browser.

     return;
+  }
   base::ThreadTaskRunnerHandle::Get()->PostDelayedTask(
       FROM_HERE,
       base::Bind(&ModelLoader::StartFetch, weak_factory_.GetWeakPtr()),
       base::TimeDelta::FromMilliseconds(delay_ms));
 }
 
 void ModelLoader::CancelFetcher() {
   // Invalidate any scheduled request.
   weak_factory_.InvalidateWeakPtrs();
   // Cancel any request in progress.
-  fetcher_.reset();
+  if (fetcher_)

[mattm, 2017/01/30 20:23:13]

unnecessary

[maksims (do not use this acc), 2017/01/31 05:50:28]

Done.

+    fetcher_.reset();
 }
 
 }  // namespace safe_browsing