predictors: Add a origin for prefetch requests, remove the URL/host settings.

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 cfb422ce1fb715c8bb9c42e486e3043914e94d31..3b60b4371614ada5faf2048f6f1777d75bef0cb5 100644
--- a/chrome/browser/predictors/resource_prefetch_common.h
+++ b/chrome/browser/predictors/resource_prefetch_common.h
@@ -59,30 +59,28 @@ struct NavigationID {
   base::TimeTicks creation_time;
 };
 
-// Represents the config for the resource prefetch prediction algorithm. It is
-// useful for running experiments.
+// Represents the config for the resource prefetch prediction algorithm.
 struct ResourcePrefetchPredictorConfig {
   // Initializes the config with default values.
   ResourcePrefetchPredictorConfig();
   ResourcePrefetchPredictorConfig(const ResourcePrefetchPredictorConfig& other);
   ~ResourcePrefetchPredictorConfig();
 
+  // Indicates what caused the prefetch request.
+  enum Origin { ORIGIN_NAVIGATION = 0, ORIGIN_EXTERNAL = 1 };

[pasko, 2016/11/29 14:44:44]

Please move it out of ResourcePrefetchPredictorConfig, the clients of this enum
do not have to know what the config is, right?

Reducing namespace pollution is still recommended with scoped enums, like:

enum class PrefetchOrigin {
  NAVIGATION,
  EXTERNAL
};

[Benoit L, 2016/11/29 17:02:51]

Done.

+
   // The mode the prefetcher is running in. Forms a bit map.
   enum Mode {
-    URL_LEARNING = 1 << 0,
-    HOST_LEARNING = 1 << 1,
-    URL_PREFETCHING = 1 << 2,  // Should also turn on URL_LEARNING.
-    HOST_PREFETCHING = 1 << 3  // Should also turn on HOST_LEARNING.
+    LEARNING = 1 << 0,
+    PREFETCHING_FOR_NAVIGATION = 1 << 2,  // Also enables LEARNING.
+    PREFETCHING_FOR_EXTERNAL = 1 << 3     // Also enables LEARNING.
   };
   int mode;
 
   // Helpers to deal with mode.
   bool IsLearningEnabled() const;
-  bool IsPrefetchingEnabled(Profile* profile) const;
-  bool IsURLLearningEnabled() const;
-  bool IsHostLearningEnabled() const;
-  bool IsURLPrefetchingEnabled(Profile* profile) const;
-  bool IsHostPrefetchingEnabled(Profile* profile) const;
+  bool IsAnyPrefetchingEnabled(Profile* profile) const;
+  bool IsPrefetchingEnabled(Profile* profile, Origin origin) const;

[pasko, 2016/11/29 14:44:44]

how about:

IsPrefetchingEnabledForOrigin(profile, origin),
IsPrefetchingEnabledForSomeOrigin(profile)

Otherwise the names did not clearly explain what the functions do (parameters
explain better, but I think my suggestion is even better)

Alternatively, remove the useless comment above the declaration of the 3
functions, and replace with more detailed comments for these including what they
do with |origin|.

[Benoit L, 2016/11/29 17:02:51]

Done.

 
   bool IsLowConfidenceForTest() const;
   bool IsHighConfidenceForTest() const;