Multi-strategy based tracking.

chrome/browser/prefs/pref_hash_store.h

Index: chrome/browser/prefs/pref_hash_store.h
diff --git a/chrome/browser/prefs/pref_hash_store.h b/chrome/browser/prefs/pref_hash_store.h
index ebef8c0b2bceba521a763fc6a0e75ea3d2ec893e..c3558086e47017849d436570221e13061650ce72 100644
--- a/chrome/browser/prefs/pref_hash_store.h
+++ b/chrome/browser/prefs/pref_hash_store.h
@@ -6,12 +6,12 @@
 #define CHROME_BROWSER_PREFS_PREF_HASH_STORE_H_
 
 #include <string>
+#include <vector>
 
 #include "base/memory/scoped_ptr.h"
 
-class PrefHashTracker;
-
 namespace base {
+class DictionaryValue;
 class Value;
 }  // namespace base
 
@@ -41,9 +41,25 @@ class PrefHashStore {
   virtual ValueState CheckValue(
       const std::string& path, const base::Value* initial_value) const = 0;
 
-  // Stores a hash of the current value of the preference at |path|.
+  // Stores a hash of the current |value| of the preference at |path|.
   virtual void StoreHash(const std::string& path,
                          const base::Value* value) = 0;
+
+  // Checks |initial_value| against the existing stored hashes for the split
+  // preference at |path|. |initial_split_value| being an empty dictionary or
+  // NULL is treated as equivalent. |invalid_keys| must initially be empty.
+  // If the return value is CHANGED: |invalid_keys| will be filled with the keys
+  // that are considered invalid (unknown or changed). |invalid_keys| will not
+  // be modified in all other cases.

[erikwright (departed), 2013/12/19 15:21:28]

'in all other cases' -> 'otherwise' or 'any other cases'.

[gab, 2013/12/20 18:37:06]

Done.

+  virtual ValueState CheckSplitValue(
+      const std::string& path,
+      const base::DictionaryValue* initial_split_value,
+      std::vector<std::string>* invalid_keys) const = 0;
+
+  // Stores hashes for the |value| of the split preference at |path|.

[erikwright (departed), 2013/12/19 15:21:28]

Are empty/null equivalent here too?

[gab, 2013/12/20 18:37:06]

Yes, clarified.

+  virtual void StoreSplitHash(
+      const std::string& path,
+      const base::DictionaryValue* split_value) = 0;
 };
 
 #endif  // CHROME_BROWSER_PREFS_PREF_HASH_STORE_H_