predictors: Enable origin learning with a flag.

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 627dab0754205a7065ce8b62c525c91482ae6d7f..f74c8b5e6de647f4a21a37df5f8c7f89ba0e6834 100644
--- a/chrome/browser/predictors/resource_prefetch_common.h
+++ b/chrome/browser/predictors/resource_prefetch_common.h
@@ -27,6 +27,7 @@ extern const char kExternalPrefetchingMode[];
 extern const char kPrefetchingMode[];
 extern const char kEnableUrlLearningParamName[];
 extern const char kEnableManifestsParamName[];
+extern const char kEnableOriginLearningParamName[];
 extern const base::Feature kSpeculativeResourcePrefetchingFeature;
 
 struct ResourcePrefetchPredictorConfig;
@@ -131,8 +132,8 @@ struct ResourcePrefetchPredictorConfig {
   bool is_url_learning_enabled;
   // True iff the predictor could use manifests.
   bool is_manifests_enabled;
-  // True iff the origin-based prediction is enabled.
-  bool is_origin_prediction_enabled;
+  // True iff origin-based learning is enabled.
+  bool is_origin_learning_enabled;
 };
 
 }  // namespace predictors