Move preference MACs to the protected preference stores.

(1) 1-time migration of MACs from local state to Preferences/Protected Preferences.
(2) Migrate MACs between Preferences/Protected Preferences according to configuration changes.

Proposed follow-up tasks are:

(1) Introduce TrackedPreferencesMigrationDelegate
(2) Introduce protections to prevent unintended stamping of the super MAC.
(3) Expanded test coverage of PrefHashFilter
(4) Expanded test coverage for legacy migration in TrackedPreferencesMigrationTest

BUG=372547, 368480
R=asvitkine@chromium.org, gab@chromium.org

Review URL: https://codereview.chromium.org/324493002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@278164 0039d316-1c4b-4281-b951-d872f2087c98

6 files changed, 28 insertions, 13 deletions

diff --git a/base/prefs/json_pref_store_unittest.cc b/base/prefs/json_pref_store_unittest.cc
index 4c9c847..2b4a9e8 100644
--- a/base/prefs/json_pref_store_unittest.cc
+++ b/base/prefs/json_pref_store_unittest.cc
@@ -40,7 +40,7 @@ class InterceptingPrefFilter : public PrefFilter {
       scoped_ptr<base::DictionaryValue> pref_store_contents) OVERRIDE;
   virtual void FilterUpdate(const std::string& path) OVERRIDE {}
   virtual void FilterSerializeData(
-      const base::DictionaryValue* pref_store_contents) OVERRIDE {}
+      base::DictionaryValue* pref_store_contents) OVERRIDE {}
 
   bool has_intercepted_prefs() const { return intercepted_prefs_ != NULL; }
 
diff --git a/base/prefs/persistent_pref_store.h b/base/prefs/persistent_pref_store.h
index 11d2a54..fb9d6dc 100644
--- a/base/prefs/persistent_pref_store.h
+++ b/base/prefs/persistent_pref_store.h
@@ -46,16 +46,6 @@ class BASE_PREFS_EXPORT PersistentPrefStore : public WriteablePrefStore {
     virtual void OnError(PrefReadError error) = 0;
   };
 
-  // Equivalent to PrefStore::GetValue but returns a mutable value.
-  virtual bool GetMutableValue(const std::string& key,
-                               base::Value** result) = 0;
-
-  // Triggers a value changed notification. This function needs to be called
-  // if one retrieves a list or dictionary with GetMutableValue and change its
-  // value. SetValue takes care of notifications itself. Note that
-  // ReportValueChanged will trigger notifications even if nothing has changed.
-  virtual void ReportValueChanged(const std::string& key) = 0;
-
   // Same as SetValue, but doesn't generate notifications. This is used by
   // PrefService::GetMutableUserPref() in order to put empty entries
   // into the user pref store. Using SetValue is not an option since existing
diff --git a/base/prefs/pref_filter.h b/base/prefs/pref_filter.h
index 1020029..82a44c6 100644
--- a/base/prefs/pref_filter.h
+++ b/base/prefs/pref_filter.h
@@ -45,9 +45,11 @@ class BASE_PREFS_EXPORT PrefFilter {
   virtual void FilterUpdate(const std::string& path) = 0;
 
   // Receives notification when the pref store is about to serialize data
-  // contained in |pref_store_contents| to a string.
+  // contained in |pref_store_contents| to a string. Modifications to
+  // |pref_store_contents| will be persisted to disk and also affect the
+  // in-memory state.
   virtual void FilterSerializeData(
-      const base::DictionaryValue* pref_store_contents) = 0;
+      base::DictionaryValue* pref_store_contents) = 0;
 };
 
 #endif  // BASE_PREFS_PREF_FILTER_H_
diff --git a/base/prefs/value_map_pref_store.cc b/base/prefs/value_map_pref_store.cc
index 0751469..5e890e2 100644
--- a/base/prefs/value_map_pref_store.cc
+++ b/base/prefs/value_map_pref_store.cc
@@ -38,6 +38,15 @@ void ValueMapPrefStore::RemoveValue(const std::string& key) {
     FOR_EACH_OBSERVER(Observer, observers_, OnPrefValueChanged(key));
 }
 
+bool ValueMapPrefStore::GetMutableValue(const std::string& key,
+                                        base::Value** value) {
+  return prefs_.GetValue(key, value);
+}
+
+void ValueMapPrefStore::ReportValueChanged(const std::string& key) {
+  FOR_EACH_OBSERVER(Observer, observers_, OnPrefValueChanged(key));
+}
+
 ValueMapPrefStore::~ValueMapPrefStore() {}
 
 void ValueMapPrefStore::NotifyInitializationCompleted() {
diff --git a/base/prefs/value_map_pref_store.h b/base/prefs/value_map_pref_store.h
index 29d0b382..c202725 100644
--- a/base/prefs/value_map_pref_store.h
+++ b/base/prefs/value_map_pref_store.h
@@ -30,6 +30,9 @@ class BASE_PREFS_EXPORT ValueMapPrefStore : public WriteablePrefStore {
   // WriteablePrefStore overrides:
   virtual void SetValue(const std::string& key, base::Value* value) OVERRIDE;
   virtual void RemoveValue(const std::string& key) OVERRIDE;
+  virtual bool GetMutableValue(const std::string& key,
+                               base::Value** value) OVERRIDE;
+  virtual void ReportValueChanged(const std::string& key) OVERRIDE;
 
  protected:
   virtual ~ValueMapPrefStore();
diff --git a/base/prefs/writeable_pref_store.h b/base/prefs/writeable_pref_store.h
index c24af95..908d867 100644
--- a/base/prefs/writeable_pref_store.h
+++ b/base/prefs/writeable_pref_store.h
@@ -26,6 +26,17 @@ class BASE_PREFS_EXPORT WriteablePrefStore : public PrefStore {
   // Removes the value for |key|.
   virtual void RemoveValue(const std::string& key) = 0;
 
+  // Equivalent to PrefStore::GetValue but returns a mutable value.
+  virtual bool GetMutableValue(const std::string& key,
+                               base::Value** result) = 0;
+
+  // Triggers a value changed notification. This function needs to be called
+  // if one retrieves a list or dictionary with GetMutableValue and change its
+  // value. SetValue takes care of notifications itself. Note that
+  // ReportValueChanged will trigger notifications even if nothing has changed.
+  virtual void ReportValueChanged(const std::string& key) = 0;
+
+
  protected:
   virtual ~WriteablePrefStore() {}