Use PrefChangeRegistrar everywhere

chrome/browser/gtk/gtk_theme_provider.cc

Index: chrome/browser/gtk/gtk_theme_provider.cc
diff --git a/chrome/browser/gtk/gtk_theme_provider.cc b/chrome/browser/gtk/gtk_theme_provider.cc
index 7e5a2c2b94231b5600124ef3f9154ea8324d3713..5bcd8a323214ef16f0d02e2066e0257416259127 100644
--- a/chrome/browser/gtk/gtk_theme_provider.cc
+++ b/chrome/browser/gtk/gtk_theme_provider.cc
@@ -258,7 +258,6 @@ GtkThemeProvider::GtkThemeProvider()
 }
 
 GtkThemeProvider::~GtkThemeProvider() {
-  profile()->GetPrefs()->RemovePrefObserver(prefs::kUsesSystemTheme, this);
   gtk_widget_destroy(fake_window_);
   gtk_widget_destroy(fake_frame_);
   fake_label_.Destroy();
@@ -273,7 +272,8 @@ GtkThemeProvider::~GtkThemeProvider() {
 }
 
 void GtkThemeProvider::Init(Profile* profile) {
-  profile->GetPrefs()->AddPrefObserver(prefs::kUsesSystemTheme, this);
+  registrar_.Init(profile->GetPrefs());
+  registrar_.Add(prefs::kUsesSystemTheme, this);
   use_gtk_ = profile->GetPrefs()->GetBoolean(prefs::kUsesSystemTheme);
 
   BrowserThemeProvider::Init(profile);