Remove the last usages of PrefObserver outside of Prefs.

chrome/browser/plugins/plugin_status_pref_setter.cc

Index: chrome/browser/plugins/plugin_status_pref_setter.cc
diff --git a/chrome/browser/plugins/plugin_status_pref_setter.cc b/chrome/browser/plugins/plugin_status_pref_setter.cc
index 2de85470fbcf802ec032c3f0126116dbd031ccbd..b9113c7e44b1b8a6530470c5dc445c833ae21d5e 100644
--- a/chrome/browser/plugins/plugin_status_pref_setter.cc
+++ b/chrome/browser/plugins/plugin_status_pref_setter.cc
@@ -27,8 +27,9 @@ PluginStatusPrefSetter::PluginStatusPrefSetter()
 PluginStatusPrefSetter::~PluginStatusPrefSetter() {
 }
 
-void PluginStatusPrefSetter::Init(Profile* profile,
-                                  PrefObserver* observer) {
+void PluginStatusPrefSetter::Init(
+    Profile* profile,
+    const BooleanPrefMember::NamedChangeCallback& observer) {
   clear_plugin_lso_data_enabled_.Init(prefs::kClearPluginLSODataEnabled,
                                       profile->GetPrefs(), observer);
   pepper_flash_settings_enabled_.Init(prefs::kPepperFlashSettingsEnabled,