Deprecate NonThreadSafe in content/renderer/media in favor of SequenceChecker.

content/renderer/media/media_stream_video_source.h

Index: content/renderer/media/media_stream_video_source.h
diff --git a/content/renderer/media/media_stream_video_source.h b/content/renderer/media/media_stream_video_source.h
index 28fa6eb8bc44476409c1c330f27925cc167f4e16..6015caf7198e214ed52172ea0a59f301262921c9 100644
--- a/content/renderer/media/media_stream_video_source.h
+++ b/content/renderer/media/media_stream_video_source.h
@@ -13,7 +13,7 @@
 #include "base/memory/weak_ptr.h"
 #include "base/message_loop/message_loop.h"
 #include "base/optional.h"
-#include "base/threading/non_thread_safe.h"
+#include "base/sequence_checker.h"
 #include "content/common/content_export.h"
 #include "content/common/media/video_capture.h"
 #include "content/renderer/media/media_stream_source.h"
@@ -46,9 +46,7 @@ CONTENT_EXPORT bool IsOldVideoConstraints();
 // MediaStreamVideoSource then match the constraints provided in AddTrack with
 // the formats and call StartSourceImpl. The source implementation must call
 // OnStartDone when the underlying source has been started or failed to start.
-class CONTENT_EXPORT MediaStreamVideoSource
-    : public MediaStreamSource,
-      NON_EXPORTED_BASE(public base::NonThreadSafe) {
+class CONTENT_EXPORT MediaStreamVideoSource : public MediaStreamSource {
  public:
   enum {
     // Default resolution. If no constraints are specified and the delegate
@@ -166,6 +164,8 @@ class CONTENT_EXPORT MediaStreamVideoSource
   };
   State state() const { return state_; }
 
+  SEQUENCE_CHECKER(sequence_checker_);
+
  private:
   void OnSupportedFormats(const media::VideoCaptureFormats& formats);