Convert enable_plugins to a buildflag header.

content/browser/android/browser_startup_controller.cc

Index: content/browser/android/browser_startup_controller.cc
diff --git a/content/browser/android/browser_startup_controller.cc b/content/browser/android/browser_startup_controller.cc
index 98b90ba95f2c376102d7593434feff3319a6a3c4..4280c6baa607fd622dcaa495a5d0c0aa5617fd02 100644
--- a/content/browser/android/browser_startup_controller.cc
+++ b/content/browser/android/browser_startup_controller.cc
@@ -7,6 +7,7 @@
 #include "base/android/jni_android.h"
 #include "base/android/jni_string.h"
 #include "content/browser/android/content_startup_flags.h"
+#include "ppapi/features/features.h"
 
 #include "jni/BrowserStartupController_jni.h"
 
@@ -57,7 +58,7 @@ static jboolean IsOfficialBuild(JNIEnv* env,
 
 static jboolean IsPluginEnabled(JNIEnv* env,
                                 const JavaParamRef<jclass>& clazz) {
-#if defined(ENABLE_PLUGINS)
+#if BUILDFLAG(ENABLE_PLUGINS)
   return true;
 #else
   return false;