predictors: Disable URL-based learning by default.

chrome/browser/predictors/resource_prefetch_common.h

 // 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.
 
 #ifndef CHROME_BROWSER_PREDICTORS_RESOURCE_PREFETCH_COMMON_H_
 #define CHROME_BROWSER_PREDICTORS_RESOURCE_PREFETCH_COMMON_H_
 
 #include <stddef.h>
 
-#include "base/feature_list.h"
 #include "base/time/time.h"
 #include "components/sessions/core/session_id.h"
 #include "url/gurl.h"
 
 class Profile;
 
 namespace content {
 class WebContents;
 }
 
 namespace predictors {
 
 extern const char kSpeculativeResourcePrefetchingFeatureName[];
 extern const char kModeParamName[];
 extern const char kLearningMode[];
 extern const char kExternalPrefetchingMode[];
 extern const char kPrefetchingMode[];
+extern const char kEnableUrlLearningParamName[];
 
 struct ResourcePrefetchPredictorConfig;
 
 // Returns true if prefetching is enabled. And will initilize the |config|
 // fields to the appropritate values.
 bool IsSpeculativeResourcePrefetchingEnabled(
     Profile* profile,
     ResourcePrefetchPredictorConfig* config);
 
 // Represents the type of key based on which prefetch data is stored.
@@ skipping 32 matching lines @@
 // Represents the config for the resource prefetch prediction algorithm.
 struct ResourcePrefetchPredictorConfig {
   // Initializes the config with default values.
   ResourcePrefetchPredictorConfig();
   ResourcePrefetchPredictorConfig(const ResourcePrefetchPredictorConfig& other);
   ~ResourcePrefetchPredictorConfig();
 
   // The mode the prefetcher is running in. Forms a bit map.
   enum Mode {
     LEARNING = 1 << 0,
-    PREFETCHING_FOR_NAVIGATION = 1 << 2,  // Also enables LEARNING.

[Benoit L, 2017/03/01 17:07:01]

nit: Why dropping the comment?

[alexilin, 2017/03/01 17:18:51]

This comment is confusing in my opinion. It should be a warning for developers
saying that it's his responsibility to enable LEARNING as well. Now it says
rather that LEARNING will be enabled automatically.
I changed wording.

-    PREFETCHING_FOR_EXTERNAL = 1 << 3     // Also enables LEARNING.
+    PREFETCHING_FOR_NAVIGATION = 1 << 2,
+    PREFETCHING_FOR_EXTERNAL = 1 << 3
   };
   int mode;
 
   // Helpers to deal with mode.
   bool IsLearningEnabled() const;
   bool IsPrefetchingEnabledForSomeOrigin(Profile* profile) const;
   bool IsPrefetchingEnabledForOrigin(Profile* profile,
                                      PrefetchOrigin origin) const;
 
   bool IsLowConfidenceForTest() const;
@@ skipping 23 matching lines @@
   // prefetched.
   float min_resource_confidence_to_trigger_prefetch;
   // The minimum number of times we must have a URL on record to prefetch it.
   size_t min_resource_hits_to_trigger_prefetch;
 
   // Maximum number of prefetches that can be inflight for a single navigation.
   size_t max_prefetches_inflight_per_navigation;
   // Maximum number of prefetches that can be inflight for a host for a single
   // navigation.
   size_t max_prefetches_inflight_per_host_per_navigation;
+  // True iff the predictor could use a url-based database.
+  bool is_url_learning_enabled;
 };
 
 }  // namespace predictors
 
 #endif  // CHROME_BROWSER_PREDICTORS_RESOURCE_PREFETCH_COMMON_H_