predictors: Disable URL-based learning by default.

chrome/browser/predictors/resource_prefetch_common.h

Index: chrome/browser/predictors/resource_prefetch_common.h
diff --git a/chrome/browser/predictors/resource_prefetch_common.h b/chrome/browser/predictors/resource_prefetch_common.h
index 3ec303d25d186fc7eced89b76116017943ed572b..778a96d4e103068dd7b5eef1a870b7f15dc23f4c 100644
--- a/chrome/browser/predictors/resource_prefetch_common.h
+++ b/chrome/browser/predictors/resource_prefetch_common.h
@@ -7,7 +7,6 @@
 
 #include <stddef.h>
 
-#include "base/feature_list.h"
 #include "base/time/time.h"
 #include "components/sessions/core/session_id.h"
 #include "url/gurl.h"
@@ -25,6 +24,7 @@ extern const char kModeParamName[];
 extern const char kLearningMode[];
 extern const char kExternalPrefetchingMode[];
 extern const char kPrefetchingMode[];
+extern const char kEnableUrlLearningParamName[];
 
 struct ResourcePrefetchPredictorConfig;
 
@@ -77,8 +77,8 @@ struct 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;
 
@@ -122,6 +122,8 @@ struct ResourcePrefetchPredictorConfig {
   // 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