Avoid creating sync token when only change is new hardware video frame.

media/filters/gpu_video_decoder.h

Index: media/filters/gpu_video_decoder.h
diff --git a/media/filters/gpu_video_decoder.h b/media/filters/gpu_video_decoder.h
index 5a609b15d03fbca60953e119679fef1d7b6e2613..478a35703c028d87fd66be1be7b2745061f783dc 100644
--- a/media/filters/gpu_video_decoder.h
+++ b/media/filters/gpu_video_decoder.h
@@ -16,6 +16,7 @@
 
 #include "base/macros.h"
 #include "base/memory/weak_ptr.h"
+#include "gpu/command_buffer/common/sync_token.h"
 #include "media/base/pipeline_status.h"
 #include "media/base/surface_manager.h"
 #include "media/base/video_decoder.h"
@@ -186,6 +187,10 @@ class MEDIA_EXPORT GpuVideoDecoder
   // steady-state of the decoder.
   std::vector<SHMBuffer*> available_shm_segments_;
 
+  // Placeholder sync token that was created and validated after the most
+  // recent picture buffers were created.
+  gpu::SyncToken sync_token_;
+
   std::map<int32_t, PendingDecoderBuffer> bitstream_buffers_in_decoder_;
   PictureBufferMap assigned_picture_buffers_;
   // PictureBuffers given to us by VDA via PictureReady, which we sent forward