Update ScopedObserver declarations in extensions directories.

This covers //c/b/ui/extensions and //c/b/extensions

These were found by attempting to compile the chrome target
on Linux.

Note that BrowserList/Observer can't be used with ScopedObserver
because Add/RemoveObserver are statics.

Bug: 998625
Change-Id: I670414cacd970fcc4c21c89689d599f94037c031
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1787991
Reviewed-by: Devlin <[email protected]>
Reviewed-by: Reilly Grant <[email protected]>
Commit-Queue: Evan Stade <[email protected]>
Cr-Commit-Position: refs/heads/master@{#694417}
diff --git a/chrome/browser/extensions/navigation_observer.cc b/chrome/browser/extensions/navigation_observer.cc
index 2e3782e..bf3303c 100644
--- a/chrome/browser/extensions/navigation_observer.cc
+++ b/chrome/browser/extensions/navigation_observer.cc
@@ -12,7 +12,6 @@
 #include "content/public/browser/notification_service.h"
 #include "content/public/browser/notification_types.h"
 #include "extensions/browser/extension_prefs.h"
-#include "extensions/browser/extension_registry.h"
 #include "extensions/browser/extension_system.h"
 
 using content::NavigationController;
@@ -25,8 +24,7 @@
 bool g_repeat_prompting = false;
 }
 
-NavigationObserver::NavigationObserver(Profile* profile)
-    : profile_(profile), extension_registry_observer_(this) {
+NavigationObserver::NavigationObserver(Profile* profile) : profile_(profile) {
   RegisterForNotifications();
   extension_registry_observer_.Add(ExtensionRegistry::Get(profile));
 }