Let chrome_prefs handle Preferences initialization from master_preferences.

chrome/browser/prefs/chrome_pref_service_factory.h

Index: chrome/browser/prefs/chrome_pref_service_factory.h
diff --git a/chrome/browser/prefs/chrome_pref_service_factory.h b/chrome/browser/prefs/chrome_pref_service_factory.h
index 371e60cadec806f50deb5fa457bcf8b3b919e247..73f6ad408bbc90842b4be84a1ecc9913d79f09df 100644
--- a/chrome/browser/prefs/chrome_pref_service_factory.h
+++ b/chrome/browser/prefs/chrome_pref_service_factory.h
@@ -9,6 +9,7 @@
 #include "base/memory/scoped_ptr.h"
 
 namespace base {
+class DictionaryValue;
 class FilePath;
 class SequencedTaskRunner;
 }
@@ -74,6 +75,12 @@ void InitializePrefHashStoreIfRequired(
 // |profile_path|.
 void ResetPrefHashStore(const base::FilePath& profile_path);
 
+// Initializes the preferences for the profile at |profile_path| with the
+// preference values in |master_prefs|. Returns true on success.
+bool InitializePrefsFromMasterPrefs(
+    const base::FilePath& profile_path,
+    const base::DictionaryValue& master_prefs);
+
 }  // namespace chrome_prefs
 
 #endif  // CHROME_BROWSER_PREFS_CHROME_PREF_SERVICE_FACTORY_H_