Use the previews black list for offline previews

components/previews/core/previews_io_data.cc

 // Copyright 2016 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 "components/previews/core/previews_io_data.h"
 
 #include "base/bind.h"
 #include "base/bind_helpers.h"
 #include "base/files/file_path.h"
 #include "base/location.h"
 #include "base/memory/ptr_util.h"
 #include "base/sequenced_task_runner.h"
 #include "base/time/default_clock.h"
 #include "components/previews/core/previews_black_list.h"
+#include "components/previews/core/previews_experiments.h"
 #include "components/previews/core/previews_opt_out_store.h"
 #include "components/previews/core/previews_ui_service.h"
+#include "net/nqe/network_quality_estimator.h"
+#include "net/url_request/url_request.h"
+#include "net/url_request/url_request_context.h"
 #include "url/gurl.h"
 
 namespace previews {
 
 PreviewsIOData::PreviewsIOData(
     const scoped_refptr<base::SingleThreadTaskRunner>& ui_task_runner,
     const scoped_refptr<base::SingleThreadTaskRunner>& io_task_runner)
     : ui_task_runner_(ui_task_runner),
       io_task_runner_(io_task_runner),
       weak_factory_(this) {}
@@ skipping 30 matching lines @@
   DCHECK(io_task_runner_->BelongsToCurrentThread());
   previews_black_list_->AddPreviewNavigation(url, opt_out, type);
 }
 
 void PreviewsIOData::ClearBlackList(base::Time begin_time,
                                     base::Time end_time) {
   DCHECK(io_task_runner_->BelongsToCurrentThread());
   previews_black_list_->ClearBlackList(begin_time, end_time);
 }
 
+bool PreviewsIOData::ShouldAllowPreview(const net::URLRequest& request,
+                                        PreviewsType type) const {
+  if (!IsOfflinePreviewsEnabled())
+    return false;
+  if (!previews_black_list_ ||
+      !previews_black_list_->IsLoadedAndAllowed(request.url(), type)) {

[tbansal1, 2016/10/06 14:55:52]

Also, how does a host that is blacklisted gets off the blacklist? e.g., one
naive approach could be that show a previews with probability = 0.1 (just an
example) even if the host is blacklisted. Then, depending on the user's opt-out
interaction, the host may automatically be removed from the blacklist.

This is probably outside the scope of this CL, but in that case it might be
useful to add a TODO here.

[RyanSturm, 2016/10/06 15:52:16]

It's a timing mechanism (90 days I believe) controlled by field trial. If the
host's last opt out was x days ago, we allow the site to be shown.

+    return false;
+  }
+  net::NetworkQualityEstimator* network_quality_estimator =
+      request.context()->network_quality_estimator();
+  if (!network_quality_estimator)
+    return false;
+
+  net::EffectiveConnectionType effective_connection_type =
+      network_quality_estimator->GetEffectiveConnectionType();
+  return effective_connection_type >= net::EFFECTIVE_CONNECTION_TYPE_OFFLINE &&
+         effective_connection_type <= net::EFFECTIVE_CONNECTION_TYPE_SLOW_2G;
+}
+
 }  // namespace previews