Replace deprecated base::NonThreadSafe in /media/audio in favor of SequenceChecker.

media/audio/audio_output_proxy.h

Index: media/audio/audio_output_proxy.h
diff --git a/media/audio/audio_output_proxy.h b/media/audio/audio_output_proxy.h
index 16a062824ea55d81aaf86c00dea8907d9307ef3f..d68622f84b6412b830528690ee201a0175006075 100644
--- a/media/audio/audio_output_proxy.h
+++ b/media/audio/audio_output_proxy.h
@@ -8,7 +8,7 @@
 #include "base/compiler_specific.h"
 #include "base/macros.h"
 #include "base/memory/weak_ptr.h"
-#include "base/threading/non_thread_safe.h"
+#include "base/sequence_checker.h"
 #include "media/audio/audio_io.h"
 #include "media/base/audio_parameters.h"
 
@@ -24,9 +24,7 @@ class AudioOutputDispatcher;
 //
 // AudioOutputProxy uses AudioOutputDispatcher to open and close
 // physical output streams.
-class MEDIA_EXPORT AudioOutputProxy
-  : public AudioOutputStream,
-    public NON_EXPORTED_BASE(base::NonThreadSafe) {
+class MEDIA_EXPORT AudioOutputProxy : public AudioOutputStream {
  public:
   // Caller keeps ownership of |dispatcher|.
   explicit AudioOutputProxy(base::WeakPtr<AudioOutputDispatcher> dispatcher);
@@ -62,6 +60,8 @@ class MEDIA_EXPORT AudioOutputProxy
   // is stopped, and then started again.
   double volume_;
 
+  SEQUENCE_CHECKER(sequence_checker_);
+
   DISALLOW_COPY_AND_ASSIGN(AudioOutputProxy);
 };