Disallow showing offline previews on a reload.

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/metrics/histogram.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_opt_out_store.h"
 #include "components/previews/core/previews_ui_service.h"
+#include "net/base/load_flags.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 {
 
 namespace {
 
 void LogPreviewsEligibilityReason(PreviewsEligibilityReason status,
@@ skipping 82 matching lines @@
     LogPreviewsEligibilityReason(
         PreviewsEligibilityReason::NETWORK_QUALITY_UNAVAILABLE, type);
     return false;
   }
   if (network_quality_estimator->GetEffectiveConnectionType() >
       net::EFFECTIVE_CONNECTION_TYPE_SLOW_2G) {
     LogPreviewsEligibilityReason(PreviewsEligibilityReason::NETWORK_NOT_SLOW,
                                  type);
     return false;
   }
+  // LOAD_VALIDATE_CACHE and LOAD_BYPASS_CACHE mean the user reloaded the page.

[tbansal1, 2016/12/12 19:52:21]

s/and/or/

Also, I am not sure if the statement is correct. There might be some other uses
of these 2 flags besides reload (e.g., forward-backward or tab restore). May be
not today, but in future? Might be better to name the enum more generically.

[RyanSturm, 2016/12/12 22:42:15]

Done.
SKIP_CACHE_VALIDATION is forward/back. I think the enum is appropriately named,
as the intention is to prevent reload-esque main frame requests.

+  // If this is a query for offline previews, reloads should be disallowed.
+  if (type == PreviewsType::OFFLINE &&
+      request.load_flags() &
+          (net::LOAD_VALIDATE_CACHE | net::LOAD_BYPASS_CACHE)) {
+    LogPreviewsEligibilityReason(
+        PreviewsEligibilityReason::RELOAD_DISALLOWED_FOR_OFFLINE, type);
+    return false;
+  }
   LogPreviewsEligibilityReason(PreviewsEligibilityReason::ALLOWED, type);
   return true;
 }
 
 }  // namespace previews