Convert enable_plugins to a buildflag header.

chrome/browser/extensions/browser_context_keyed_service_factories.cc

Index: chrome/browser/extensions/browser_context_keyed_service_factories.cc
diff --git a/chrome/browser/extensions/browser_context_keyed_service_factories.cc b/chrome/browser/extensions/browser_context_keyed_service_factories.cc
index 50cd87bb48ad7cb3d4cfa5fa86d2e8cf97d64e4a..f1169e203dceaef66661bfda2eb3d341743fc0bb 100644
--- a/chrome/browser/extensions/browser_context_keyed_service_factories.cc
+++ b/chrome/browser/extensions/browser_context_keyed_service_factories.cc
@@ -55,6 +55,7 @@
 #include "chrome/common/features.h"
 #include "components/spellcheck/spellcheck_build_features.h"
 #include "extensions/browser/api/bluetooth_low_energy/bluetooth_low_energy_api.h"
+#include "ppapi/features/features.h"
 
 #if defined(OS_CHROMEOS)
 #include "chrome/browser/chromeos/extensions/file_manager/event_router_factory.h"
@@ -126,7 +127,7 @@ void EnsureBrowserContextKeyedServiceFactoriesBuilt() {
   extensions::MenuManagerFactory::GetInstance();
   extensions::OmniboxAPI::GetFactoryInstance();
   extensions::PasswordsPrivateEventRouterFactory::GetInstance();
-#if defined(ENABLE_PLUGINS)
+#if BUILDFLAG(ENABLE_PLUGINS)
   extensions::PluginManager::GetFactoryInstance();
 #endif
   extensions::PreferenceAPI::GetFactoryInstance();