Convert enable_plugins to a buildflag header.

chrome/browser/android/tab_web_contents_delegate_android.cc

Index: chrome/browser/android/tab_web_contents_delegate_android.cc
diff --git a/chrome/browser/android/tab_web_contents_delegate_android.cc b/chrome/browser/android/tab_web_contents_delegate_android.cc
index 746128c918838baabdfd5935d6e24a58304a6751..9074acfe6329de24a2eeff4255d575f074e1fb83 100644
--- a/chrome/browser/android/tab_web_contents_delegate_android.cc
+++ b/chrome/browser/android/tab_web_contents_delegate_android.cc
@@ -41,11 +41,12 @@
 #include "content/public/browser/web_contents.h"
 #include "content/public/common/file_chooser_params.h"
 #include "jni/TabWebContentsDelegateAndroid_jni.h"
+#include "ppapi/features/features.h"
 #include "third_party/WebKit/public/web/WebWindowFeatures.h"
 #include "ui/gfx/geometry/rect.h"
 #include "ui/gfx/geometry/rect_f.h"
 
-#if defined(ENABLE_PLUGINS)
+#if BUILDFLAG(ENABLE_PLUGINS)
 #include "chrome/browser/pepper_broker_infobar_delegate.h"
 #endif
 
@@ -286,7 +287,7 @@ bool TabWebContentsDelegateAndroid::RequestPpapiBrokerPermission(
     const GURL& url,
     const base::FilePath& plugin_path,
     const base::Callback<void(bool)>& callback) {
-#if defined(ENABLE_PLUGINS)
+#if BUILDFLAG(ENABLE_PLUGINS)
     PepperBrokerInfoBarDelegate::Create(
         web_contents, url, plugin_path, callback);
     return true;