Move enable extensions define to a build flag.

chrome/browser/ui/webui/net_internals/net_internals_ui.cc

Index: chrome/browser/ui/webui/net_internals/net_internals_ui.cc
diff --git a/chrome/browser/ui/webui/net_internals/net_internals_ui.cc b/chrome/browser/ui/webui/net_internals/net_internals_ui.cc
index 33908b734c10091c9cb95c575fec480a01e7dd36..1e821dcf9bdebbd7b6bee3e1f59cc4f8f31419a5 100644
--- a/chrome/browser/ui/webui/net_internals/net_internals_ui.cc
+++ b/chrome/browser/ui/webui/net_internals/net_internals_ui.cc
@@ -65,6 +65,7 @@
 #include "content/public/browser/web_ui.h"
 #include "content/public/browser/web_ui_data_source.h"
 #include "content/public/browser/web_ui_message_handler.h"
+#include "extensions/features/features.h"
 #include "net/base/net_errors.h"
 #include "net/disk_cache/disk_cache.h"
 #include "net/dns/host_cache.h"
@@ -100,7 +101,7 @@
 #include "chrome/browser/net/service_providers_win.h"
 #endif
 
-#if defined(ENABLE_EXTENSIONS)
+#if BUILDFLAG(ENABLE_EXTENSIONS)
 #include "chrome/browser/extensions/extension_service.h"
 #include "chrome/browser/ui/webui/extensions/extension_basic_info.h"
 #include "extensions/browser/extension_registry.h"
@@ -406,7 +407,7 @@ void NetInternalsMessageHandler::RegisterMessages() {
   proxy_->AddRequestContextGetter(
       content::BrowserContext::GetDefaultStoragePartition(profile)->
           GetMediaURLRequestContext());
-#if defined(ENABLE_EXTENSIONS)
+#if BUILDFLAG(ENABLE_EXTENSIONS)
   proxy_->AddRequestContextGetter(profile->GetRequestContextForExtensions());
 #endif
 
@@ -571,7 +572,7 @@ void NetInternalsMessageHandler::OnGetExtensionInfo(
     const base::ListValue* list) {
   DCHECK_CURRENTLY_ON(BrowserThread::UI);
   auto extension_list = base::MakeUnique<base::ListValue>();
-#if defined(ENABLE_EXTENSIONS)
+#if BUILDFLAG(ENABLE_EXTENSIONS)
   Profile* profile = Profile::FromWebUI(web_ui());
   extensions::ExtensionSystem* extension_system =
       extensions::ExtensionSystem::Get(profile);