diff --git a/atom/browser/native_window.cc b/atom/browser/native_window.cc
index 96085846bc..b0b99081e3 100644
--- a/atom/browser/native_window.cc
+++ b/atom/browser/native_window.cc
@@ -424,7 +424,6 @@ void NativeWindow::OverrideWebkitPrefs(content::WebPreferences* prefs) {
     return;
 
   bool b;
-  std::vector<base::FilePath> list;
   if (web_preferences_.Get("javascript", &b))
     prefs->javascript_enabled = b;
   if (web_preferences_.Get("images", &b))
@@ -446,14 +445,6 @@ void NativeWindow::OverrideWebkitPrefs(content::WebPreferences* prefs) {
     prefs->allow_displaying_insecure_content = b;
   if (web_preferences_.Get("allow-running-insecure-content", &b))
     prefs->allow_running_insecure_content = b;
-  if (web_preferences_.Get("extra-plugin-dirs", &list)) {
-    if (content::PluginService::GetInstance()->NPAPIPluginsSupported()) {
-      for (size_t i = 0; i < list.size(); ++i)
-        content::PluginService::GetInstance()->AddExtraPluginDir(list[i]);
-    } else {
-      LOG(WARNING) << "NPAPI plugins not supported on this platform";
-    }
-  }
 }
 
 void NativeWindow::NotifyWindowClosed() {
diff --git a/atom/browser/web_contents_preferences.cc b/atom/browser/web_contents_preferences.cc
index 8b956c1b41..fbd2c7661a 100644
--- a/atom/browser/web_contents_preferences.cc
+++ b/atom/browser/web_contents_preferences.cc
@@ -22,4 +22,11 @@ WebContentsPreferences::WebContentsPreferences(
 WebContentsPreferences::~WebContentsPreferences() {
 }
 
+// static
+WebContentsPreferences* WebContentsPreferences::From(
+    content::WebContents* web_contents) {
+  return static_cast<WebContentsPreferences*>(
+      web_contents->GetUserData(kWebPreferencesKey));
+}
+
 }  // namespace atom
diff --git a/atom/browser/web_contents_preferences.h b/atom/browser/web_contents_preferences.h
index bbbc4cf5e2..c4c50dc070 100644
--- a/atom/browser/web_contents_preferences.h
+++ b/atom/browser/web_contents_preferences.h
@@ -10,9 +10,13 @@
 
 namespace atom {
 
+// Stores and applies the preferences of WebContents.
 class WebContentsPreferences
     : public content::WebContentsUserData<WebContentsPreferences> {
  public:
+  // Get the preferences of |web_contents|.
+  static WebContentsPreferences* From(content::WebContents* web_contents);
+
   WebContentsPreferences(content::WebContents* web_contents,
                          base::DictionaryValue&& web_preferences);
   ~WebContentsPreferences() override;