Directly call ExtensionManagementFactory::GetForBrowserContext

there is no reason to call ExtensionManagementFactory::GetInstance to
access it. More, GetForBrowserContext calls GetInstance itself.

ExtensionManagementFactory: :GetForBrowserContext is a static method, so
Change-Id: Ib761361258047b144edc8c2ee725c2b1811f6697
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1724511Reviewed-by: Devlin <rdevlin.cronin@chromium.org>
Reviewed-by: Pavol Marko <pmarko@chromium.org>
Commit-Queue: Oleg Davydov <burunduk@chromium.org>
Cr-Commit-Position: refs/heads/master@{#682296}

chrome/browser/extensions/extension_management.cc

@@ -602,12 +602,14 @@ internal::IndividualSettings* ExtensionManagement::AccessByUpdateUrl(
   return settings.get();
 }
 
+// static
 ExtensionManagement* ExtensionManagementFactory::GetForBrowserContext(
     content::BrowserContext* context) {
   return static_cast<ExtensionManagement*>(
       GetInstance()->GetServiceForBrowserContext(context, true));
 }
 
+// static
 ExtensionManagementFactory* ExtensionManagementFactory::GetInstance() {
   return base::Singleton<ExtensionManagementFactory>::get();
 }

chrome/browser/extensions/extension_service.cc

@@ -376,9 +376,8 @@ ExtensionService::~ExtensionService() {
 }
 
 void ExtensionService::Shutdown() {
-  ExtensionManagementFactory::GetInstance()
-      ->GetForBrowserContext(profile())
-      ->RemoveObserver(this);
+  ExtensionManagementFactory::GetForBrowserContext(profile())->RemoveObserver(
+      this);
 }
 
 const Extension* ExtensionService::GetExtensionById(