Multi-strategy based tracking.

chrome/browser/prefs/pref_hash_filter.h

Index: chrome/browser/prefs/pref_hash_filter.h
diff --git a/chrome/browser/prefs/pref_hash_filter.h b/chrome/browser/prefs/pref_hash_filter.h
index baa7811a05aca3fd5ed75039ac5f2f8f626e780a..0232038eb0fc88a7a34c284ff4f0b1430f8789b0 100644
--- a/chrome/browser/prefs/pref_hash_filter.h
+++ b/chrome/browser/prefs/pref_hash_filter.h
@@ -12,8 +12,7 @@
 #include "base/compiler_specific.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/prefs/pref_filter.h"
-
-class PrefHashStore;
+#include "chrome/browser/prefs/pref_hash_store.h"
 
 namespace base {
 class DictionaryValue;
@@ -25,7 +24,31 @@ class Value;
 // are changed.
 class PrefHashFilter : public PrefFilter {
  public:
+  enum PrefTrackingStrategy {
+    // Do not track this preference. Used when tracking is desired on some
+    // platforms only.
+    TRACKING_STRATEGY_NONE,
+    // Atomic preferences are tracked as a whole.
+    TRACKING_STRATEGY_ATOMIC,
+    // Split preferences are dictionaries for which each top-level entry is
+    // tracked independently.
+    TRACKING_STRATEGY_SPLIT,
+  };
+
+  struct TrackedPreference {
+    const char* name;
+    PrefTrackingStrategy strategy;
+  };
+
+  // Constructs a PrefHashFilter with the default set of tracked preferences.
   explicit PrefHashFilter(scoped_ptr<PrefHashStore> pref_hash_store);
+
+  // Constructs a PrefHashFilter with the specified |tracked_preferences|. Meant
+  // to be used by tests only.
+  PrefHashFilter(scoped_ptr<PrefHashStore> pref_hash_store,
+                 const TrackedPreference tracked_preferences[],
+                 size_t tracked_preferences_size);
+
   virtual ~PrefHashFilter();
 
   // PrefFilter implementation.
@@ -35,8 +58,38 @@ class PrefHashFilter : public PrefFilter {
                             const base::Value* value) OVERRIDE;
 
  private:
+  struct TrackedPreferenceMetaData {
+    TrackedPreferenceMetaData(size_t index_in, PrefTrackingStrategy strategy_in)

[erikwright (departed), 2013/12/17 02:22:50]

The fact that it was originally an index is not important here. Call it
'reporting ID' or something.

[erikwright (departed), 2013/12/17 02:22:50]

consider whether the constructor adds anything over standard struct-literal
initialization.

[gab, 2013/12/17 18:08:05]

Done.

[gab, 2013/12/17 18:08:05]

Done.

+        : index(index_in), strategy(strategy_in) {}
+
+    // The index of this tracked preference (important for metrics reporting).

[erikwright (departed), 2013/12/17 02:22:50]

once the name changes, these comments are no longer required as they will be
self-documented.

[gab, 2013/12/17 18:08:05]

Done.

+    size_t index;
+    // The strategy used to track this preference.
+    PrefTrackingStrategy strategy;
+  };
+
+  typedef std::map<std::string, const TrackedPreferenceMetaData>
+      TrackedPreferencesMap;
+
+  /// Initializes |tracked_paths_| from |tracked_preferences_|.
+  void InitTrackedPreferences(const TrackedPreference tracked_preferences[],
+                              size_t tracked_preferences_size);
+
+  // Updates the hash(es) in |pref_hash_store_| for |value| at |path| based on
+  // the tracking |strategy|.
+  void StoreHashBasedOnStrategy(const std::string& path,

[erikwright (departed), 2013/12/17 02:22:50]

BasedOn -> Using

[gab, 2013/12/17 18:08:05]

Done.

+                                const base::Value* value,
+                                PrefTrackingStrategy strategy);
+
+  // Updates the hash(es) in |pref_hash_store_| for |value| at |path| based on
+  // the tracking |strategy|.

[erikwright (departed), 2013/12/17 02:22:50]

fix comment (Updates -> Checks)

[gab, 2013/12/17 18:08:05]

Done.

+  PrefHashStore::ValueState CheckValueBasedOnStrategy(
+      const std::string& path,
+      const base::Value* value,
+      PrefTrackingStrategy strategy);
+
   scoped_ptr<PrefHashStore> pref_hash_store_;
-  std::set<std::string> tracked_paths_;
+  TrackedPreferencesMap tracked_paths_;
 
   DISALLOW_COPY_AND_ASSIGN(PrefHashFilter);
 };