MD Settings: avoid double pref observation on Startup Pages

chrome/browser/ui/webui/settings/settings_startup_pages_handler.cc

Index: chrome/browser/ui/webui/settings/settings_startup_pages_handler.cc
diff --git a/chrome/browser/ui/webui/settings/settings_startup_pages_handler.cc b/chrome/browser/ui/webui/settings/settings_startup_pages_handler.cc
index 233df7c3022041e7d9874885b1c08b363cf80017..ed3a9341b2542943ec7d89dec3e165514308cba3 100644
--- a/chrome/browser/ui/webui/settings/settings_startup_pages_handler.cc
+++ b/chrome/browser/ui/webui/settings/settings_startup_pages_handler.cc
@@ -40,6 +40,11 @@ void StartupPagesHandler::RegisterMessages() {
                  base::Unretained(this)));
 }
 
+void StartupPagesHandler::RenderViewReused() {
+  startup_custom_pages_table_model_.SetObserver(nullptr);
+  pref_change_registrar_.RemoveAll();
+}
+
 void StartupPagesHandler::OnModelChanged() {
   base::ListValue startup_pages;
   int page_count = startup_custom_pages_table_model_.RowCount();