Remove the last usages of PrefObserver outside of Prefs.

chrome/browser/ui/views/extensions/disabled_extensions_view.cc

Index: chrome/browser/ui/views/extensions/disabled_extensions_view.cc
diff --git a/chrome/browser/ui/views/extensions/disabled_extensions_view.cc b/chrome/browser/ui/views/extensions/disabled_extensions_view.cc
index 4c2877850ef096cd8518b2a26487693064bc7ef7..c7cd4f878385ddd09c58e3150816611a03fa808d 100644
--- a/chrome/browser/ui/views/extensions/disabled_extensions_view.cc
+++ b/chrome/browser/ui/views/extensions/disabled_extensions_view.cc
@@ -80,7 +80,7 @@ void DisabledExtensionsView::MaybeShow(Browser* browser,
 
   sideload_wipeout_bubble_shown.Init(
       prefs::kExtensionsSideloadWipeoutBubbleShown,
-          browser->profile()->GetPrefs(), NULL);
+          browser->profile()->GetPrefs());
   int bubble_shown_count = sideload_wipeout_bubble_shown.GetValue();
   if (bubble_shown_count >= kShowSideloadWipeoutBubbleMax)
     return;
@@ -130,7 +130,7 @@ void DisabledExtensionsView::DismissBubble() {
   IntegerPrefMember sideload_wipeout_bubble_shown;
   sideload_wipeout_bubble_shown.Init(
       prefs::kExtensionsSideloadWipeoutBubbleShown,
-      browser_->profile()->GetPrefs(), NULL);
+      browser_->profile()->GetPrefs());
   sideload_wipeout_bubble_shown.SetValue(kShowSideloadWipeoutBubbleMax);
 
   GetWidget()->Close();