Convert enable_plugins to a buildflag header.

chrome/browser/extensions/extension_garbage_collector_chromeos_unittest.cc

Index: chrome/browser/extensions/extension_garbage_collector_chromeos_unittest.cc
diff --git a/chrome/browser/extensions/extension_garbage_collector_chromeos_unittest.cc b/chrome/browser/extensions/extension_garbage_collector_chromeos_unittest.cc
index 1496a726faf317b41fe79f90088d0b125dfd98c4..260919628b176989cda3d5578c9059f800281eda 100644
--- a/chrome/browser/extensions/extension_garbage_collector_chromeos_unittest.cc
+++ b/chrome/browser/extensions/extension_garbage_collector_chromeos_unittest.cc
@@ -33,6 +33,7 @@
 #include "extensions/browser/extension_prefs.h"
 #include "extensions/browser/install_flag.h"
 #include "extensions/common/manifest_constants.h"
+#include "ppapi/features/features.h"
 
 namespace {
 const char kExtensionId1[] = "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa";
@@ -47,7 +48,7 @@ class ExtensionGarbageCollectorChromeOSUnitTest
   const base::FilePath& cache_dir() { return cache_dir_.GetPath(); }
 
   void SetUp() override {
-#if defined(ENABLE_PLUGINS)
+#if BUILDFLAG(ENABLE_PLUGINS)
     content::PluginService::GetInstance()->Init();
 #endif
     InitializeGoodInstalledExtensionService();