Let chrome_prefs handle Preferences initialization from master_preferences.

chrome/browser/prefs/chrome_pref_service_factory.cc

Index: chrome/browser/prefs/chrome_pref_service_factory.cc
diff --git a/chrome/browser/prefs/chrome_pref_service_factory.cc b/chrome/browser/prefs/chrome_pref_service_factory.cc
index 877ab2771c272fa417865f2d2558ed3f7c66118c..4b7044f497ca12779811fe7ea7d9f8543a23c3bf 100644
--- a/chrome/browser/prefs/chrome_pref_service_factory.cc
+++ b/chrome/browser/prefs/chrome_pref_service_factory.cc
@@ -19,6 +19,7 @@
 #include "base/prefs/pref_service.h"
 #include "base/prefs/pref_store.h"
 #include "base/prefs/pref_value_store.h"
+#include "base/values.h"
 #include "chrome/browser/browser_process.h"
 #include "chrome/browser/prefs/command_line_pref_store.h"
 #include "chrome/browser/prefs/pref_hash_filter.h"
@@ -265,6 +266,32 @@ void PrepareBuilder(
           pref_filter.Pass()));
 }
 
+// An in-memory PrefStore backed by an immutable DictionaryValue.
+class DictionaryPrefStore : public PrefStore {
+ public:
+  explicit DictionaryPrefStore(const base::DictionaryValue* dictionary)
+      : dictionary_(dictionary) {}
+
+  virtual bool GetValue(const std::string& key,
+                        const base::Value** result) const OVERRIDE {
+    const base::Value* tmp = NULL;
+    if (!dictionary_->Get(key, &tmp))
+      return false;
+
+    if (result)
+      *result = tmp;
+    return true;
+  }
+
+ protected:
+  virtual ~DictionaryPrefStore() {}

[Bernhard Bauer, 2014/02/04 09:08:02]

Nit: Make the destructor private? Protected implies to me that you're intending
to subclass it.

[gab, 2014/02/04 14:01:04]

Done.

+
+ private:
+  const base::DictionaryValue* dictionary_;
+
+  DISALLOW_COPY_AND_ASSIGN(DictionaryPrefStore);
+};
+
 // Waits for a PrefStore to be initialized and then initializes the
 // corresponding PrefHashStore.
 // The observer deletes itself when its work is completed.
@@ -296,8 +323,12 @@ void InitializeHashStoreObserver::OnPrefValueChanged(const std::string& key) {}
 void InitializeHashStoreObserver::OnInitializationCompleted(bool succeeded) {
   // If we successfully loaded the preferences _and_ the PrefHashStore hasn't
   // been initialized by someone else in the meantime initialize it now.
-  if (succeeded & !pref_hash_store_->IsInitialized())
-    CreatePrefHashFilter(pref_hash_store_.Pass())->Initialize(pref_store_);
+  if (succeeded & !pref_hash_store_->IsInitialized()) {
+    CreatePrefHashFilter(
+        pref_hash_store_.Pass())->Initialize(*pref_store_);
+    UMA_HISTOGRAM_BOOLEAN(
+        "Settings.TrackedPreferencesInitializedForUnloadedProfile", true);
+  }
   pref_store_->RemoveObserver(this);
   delete this;
 }
@@ -346,7 +377,7 @@ scoped_ptr<PrefServiceSyncable> CreateProfilePrefs(
   return factory.CreateSyncable(pref_registry.get());
 }
 
-void InitializeHashStoreForPrefFile(
+void InitializeHashStoreFromPrefFile(
     const base::FilePath& pref_filename,
     base::SequencedTaskRunner* pref_io_task_runner,
     scoped_ptr<PrefHashStore> pref_hash_store) {
@@ -359,4 +390,12 @@ void InitializeHashStoreForPrefFile(
   pref_store->ReadPrefsAsync(NULL);
 }
 
+void InitializeHashStoreFromMasterPrefs(
+    const base::DictionaryValue& master_prefs,
+    scoped_ptr<PrefHashStore> pref_hash_store) {
+  scoped_refptr<const PrefStore> pref_store(
+      new DictionaryPrefStore(&master_prefs));
+  CreatePrefHashFilter(pref_hash_store.Pass())->Initialize(*pref_store);
+}
+
 }  // namespace chrome_prefs