Convert enable_plugins to a buildflag header.

media/base/media_switches.h

Index: media/base/media_switches.h
diff --git a/media/base/media_switches.h b/media/base/media_switches.h
index f7a2dba6af4b9a277f6e16d31976173226ab1398..13f8bfe9f9770f2ba2df3e88f96783c871972681 100644
--- a/media/base/media_switches.h
+++ b/media/base/media_switches.h
@@ -10,6 +10,7 @@
 #include "base/feature_list.h"
 #include "build/build_config.h"
 #include "media/base/media_export.h"
+#include "ppapi/features/features.h"
 
 namespace switches {
 
@@ -43,13 +44,13 @@ MEDIA_EXPORT extern const char kWaveOutBuffers[];
 MEDIA_EXPORT extern const char kUseCras[];
 #endif
 
-#if !defined(OS_ANDROID) || defined(ENABLE_PLUGINS)
+#if !defined(OS_ANDROID) || BUILDFLAG(ENABLE_PLUGINS)
 MEDIA_EXPORT extern const char kEnableDefaultMediaSession[];
-#endif  // !defined(OS_ANDROID) || defined(ENABLE_PLUGINS)
+#endif  // !defined(OS_ANDROID) || BUILDFLAG(ENABLE_PLUGINS)
 
-#if defined(ENABLE_PLUGINS)
+#if BUILDFLAG(ENABLE_PLUGINS)
 MEDIA_EXPORT extern const char kEnableDefaultMediaSessionDuckFlash[];
-#endif  // defined(ENABLE_PLUGINS)
+#endif  // BUILDFLAG(ENABLE_PLUGINS)
 
 MEDIA_EXPORT extern const char kUseFakeDeviceForMediaStream[];
 MEDIA_EXPORT extern const char kUseFileForFakeVideoCapture[];