Update ScopedObserver declarations in //extensions

Bug: 998625
Change-Id: I97a94d94e8fb0e364c0c595c2289079b7e062e83
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1785100
Reviewed-by: Reilly Grant <[email protected]>
Commit-Queue: Evan Stade <[email protected]>
Cr-Commit-Position: refs/heads/master@{#693363}
diff --git a/extensions/browser/lazy_background_task_queue.cc b/extensions/browser/lazy_background_task_queue.cc
index 523134f..b97fba1 100644
--- a/extensions/browser/lazy_background_task_queue.cc
+++ b/extensions/browser/lazy_background_task_queue.cc
@@ -13,7 +13,6 @@
 #include "content/public/browser/site_instance.h"
 #include "content/public/browser/web_contents.h"
 #include "extensions/browser/extension_host.h"
-#include "extensions/browser/extension_registry.h"
 #include "extensions/browser/extensions_browser_client.h"
 #include "extensions/browser/lazy_background_task_queue_factory.h"
 #include "extensions/browser/lazy_context_id.h"
@@ -43,7 +42,7 @@
 
 LazyBackgroundTaskQueue::LazyBackgroundTaskQueue(
     content::BrowserContext* browser_context)
-    : browser_context_(browser_context), extension_registry_observer_(this) {
+    : browser_context_(browser_context) {
   registrar_.Add(this,
                  extensions::NOTIFICATION_EXTENSION_HOST_DID_STOP_FIRST_LOAD,
                  content::NotificationService::AllBrowserContextsAndSources());