ui: Cleanup class/struct forward declarations

media/midi/midi_switches.cc

Index: media/midi/midi_switches.cc
diff --git a/media/midi/midi_switches.cc b/media/midi/midi_switches.cc
index 47ba28ea49c8132d1559588c170c4005a23bda8b..fa00af305f639b3dfeb15d81099b505012d18024 100644
--- a/media/midi/midi_switches.cc
+++ b/media/midi/midi_switches.cc
@@ -5,18 +5,14 @@
 #include "build/build_config.h"
 #include "media/midi/midi_switches.h"
 
-namespace switches {
+namespace midi {
+namespace features {
 
 #if defined(OS_ANDROID)
-// Use Android Midi API for WebMIDI
-const char kUseAndroidMidiApi[] = "use-android-midi-api";
+const base::Feature kMidiManagerAndroid{"MidiManagerAndroid",
+                                        base::FEATURE_ENABLED_BY_DEFAULT};
 #endif
 
-}  // namespace switches
-
-namespace midi {
-namespace features {
-
 #if defined(OS_WIN)
 const base::Feature kMidiManagerWinrt{"MidiManagerWinrt",
                                       base::FEATURE_DISABLED_BY_DEFAULT};