Detach the dependency from host_content_settings_map to extension.

chrome/browser/content_settings/content_settings_pref_provider.cc

Index: chrome/browser/content_settings/content_settings_pref_provider.cc
diff --git a/chrome/browser/content_settings/content_settings_pref_provider.cc b/chrome/browser/content_settings/content_settings_pref_provider.cc
index 0046dd303dc54597e1d1921869334d115c873ca0..f0697a89657b211c9b19d2f5a3df7fbf1091d8b0 100644
--- a/chrome/browser/content_settings/content_settings_pref_provider.cc
+++ b/chrome/browser/content_settings/content_settings_pref_provider.cc
@@ -567,6 +567,14 @@ void PrefProvider::ShutdownOnUIThread() {
   prefs_ = NULL;
 }
 
+std::string PrefProvider::GetProviderName() const {
+  return "preference";
+}
+
+SettingSource PrefProvider::GetSettingSource() const {
+  return SETTING_SOURCE_USER;
+}
+
 void PrefProvider::UpdateLastUsage(
     const ContentSettingsPattern& primary_pattern,
     const ContentSettingsPattern& secondary_pattern,