Pref service: Add a ScopedDictionaryPrefUpdate to track value changes.

components/prefs/writeable_pref_store.h

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef COMPONENTS_PREFS_WRITEABLE_PREF_STORE_H_
 #define COMPONENTS_PREFS_WRITEABLE_PREF_STORE_H_
 
 #include <stdint.h>
 
 #include <memory>
+#include <set>
 #include <string>
+#include <vector>
 
 #include "base/macros.h"
 #include "components/prefs/pref_store.h"
 
 namespace base {
 class Value;
 }
 
 // A pref store that can be written to as well as read from.
 class COMPONENTS_PREFS_EXPORT WriteablePrefStore : public PrefStore {
@@ skipping 17 matching lines @@
                         std::unique_ptr<base::Value> value,
                         uint32_t flags) = 0;
 
   // Removes the value for |key|.
   virtual void RemoveValue(const std::string& key, uint32_t flags) = 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.
-  // |flags| is a bitmask of PrefWriteFlags.
+  // Triggers a value changed notification. This function or
+  // ReportSubValuesChanged 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.  |flags| is a bitmask of
+  // PrefWriteFlags.
   virtual void ReportValueChanged(const std::string& key, uint32_t flags) = 0;
 
+  // Triggers a value changed notification for |path_components| in the |key|
+  // pref. This function or ReportValueChanged 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
+  // ReportSubValuesChanged will trigger notifications even if nothing has
+  // changed. |flags| is a bitmask of PrefWriteFlags.
+  virtual void ReportSubValuesChanged(
+      const std::string& key,
+      std::set<std::vector<std::string>> path_components,
+      uint32_t flags);
+
   // 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
   // tests rely on the number of notifications generated. |flags| is a bitmask
   // of PrefWriteFlags.
   virtual void SetValueSilently(const std::string& key,
                                 std::unique_ptr<base::Value> value,
                                 uint32_t flags) = 0;
 
  protected:
   ~WriteablePrefStore() override {}
 
  private:
   DISALLOW_COPY_AND_ASSIGN(WriteablePrefStore);
 };
 
 #endif  // COMPONENTS_PREFS_WRITEABLE_PREF_STORE_H_