predictors: Add an about:flags flag for speculative prefetch.

chrome/browser/predictors/resource_prefetch_common.cc

 // Copyright 2014 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/predictors/resource_prefetch_common.h"
 
 #include <string>
 #include <tuple>
 
-#include "base/feature_list.h"
 #include "base/metrics/field_trial_params.h"
 #include "chrome/browser/net/prediction_options.h"
 #include "chrome/browser/profiles/profile.h"
 #include "chrome/browser/sessions/session_tab_helper.h"
 #include "components/prefs/pref_service.h"
 #include "content/public/browser/browser_thread.h"
 #include "content/public/browser/web_contents.h"
 
 namespace predictors {
 
 const char kSpeculativeResourcePrefetchingFeatureName[] =
     "SpeculativeResourcePrefetching";
 const char kModeParamName[] = "mode";
 const char kLearningMode[] = "learning";
 const char kExternalPrefetchingMode[] = "external-prefetching";
 const char kPrefetchingMode[] = "prefetching";
 const char kEnableUrlLearningParamName[] = "enable-url-learning";
 
+const base::Feature kSpeculativeResourcePrefetchingFeature =
+    base::Feature(kSpeculativeResourcePrefetchingFeatureName,
+                  base::FEATURE_DISABLED_BY_DEFAULT);
+
 namespace {
 
-const base::Feature kSpeculativeResourcePrefetchingFeature{
-    kSpeculativeResourcePrefetchingFeatureName,
-    base::FEATURE_DISABLED_BY_DEFAULT};
-
 bool IsPrefetchingEnabledInternal(Profile* profile, int mode, int mask) {
   DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
   if ((mode & mask) == 0)
     return false;
 
   if (!profile || !profile->GetPrefs() ||
       chrome_browser_net::CanPrefetchAndPrerenderUI(profile->GetPrefs()) !=
           chrome_browser_net::NetworkPredictionStatus::ENABLED) {
     return false;
   }
@@ skipping 135 matching lines @@
 
 bool ResourcePrefetchPredictorConfig::IsMoreResourcesEnabledForTest() const {
   return max_resources_per_entry == 100;
 }
 
 bool ResourcePrefetchPredictorConfig::IsSmallDBEnabledForTest() const {
   return max_urls_to_track == 200 && max_hosts_to_track == 100;
 }
 
 }  // namespace predictors