Replace deprecated base::NonThreadSafe in extensions/browser/api/cast_channel in favor of SequenceC…

extensions/browser/api/cast_channel/cast_transport.h

Index: extensions/browser/api/cast_channel/cast_transport.h
diff --git a/extensions/browser/api/cast_channel/cast_transport.h b/extensions/browser/api/cast_channel/cast_transport.h
index d4e5805254641b7e9ec22080c2d7c3d33cfc52b0..ba67ee8f1d77028602b9c8f497795abdf96b0199 100644
--- a/extensions/browser/api/cast_channel/cast_transport.h
+++ b/extensions/browser/api/cast_channel/cast_transport.h
@@ -10,7 +10,7 @@
 
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
-#include "base/threading/non_thread_safe.h"
+#include "base/sequence_checker.h"
 #include "base/threading/thread_checker.h"
 #include "extensions/browser/api/cast_channel/logger.h"
 #include "extensions/common/api/cast_channel.h"
@@ -72,7 +72,7 @@ class CastTransport {
 };
 
 // Manager class for reading and writing messages to/from a socket.
-class CastTransportImpl : public CastTransport, public base::NonThreadSafe {
+class CastTransportImpl : public CastTransport {
  public:
   // Adds a CastMessage read/write layer to a socket.
   // Message read events are propagated to the owner via |read_delegate|.
@@ -215,6 +215,8 @@ class CastTransportImpl : public CastTransport, public base::NonThreadSafe {
   // Accumulates details of events and errors, for debugging purposes.
   scoped_refptr<Logger> logger_;
 
+  SEQUENCE_CHECKER(sequence_checker_);
+
   DISALLOW_COPY_AND_ASSIGN(CastTransportImpl);
 };
 }  // namespace cast_channel