Removing unused field in DXVAVideoDecodeAccelerator

Some jumbo build configurations would not compile because of
the unused field. The are not allowed by the build system but
sometimes only jumbo builds notice such things since they
have access to more source code.

Cq-Include-Trybots: luci.chromium.try:android_optional_gpu_tests_rel;luci.chromium.try:linux_optional_gpu_tests_rel;luci.chromium.try:mac_optional_gpu_tests_rel;luci.chromium.try:win_optional_gpu_tests_rel
Change-Id: I079412fc98e5812f709b6566d02de9d91a5a8706
Reviewed-on: https://chromium-review.googlesource.com/1249485Reviewed-by: Frank Liberato <liberato@chromium.org>
Commit-Queue: Daniel Bratell <bratell@opera.com>
Cr-Commit-Position: refs/heads/master@{#594759}

media/gpu/windows/dxva_video_decode_accelerator_win.h

@@ -418,8 +418,6 @@ class MEDIA_GPU_EXPORT DXVAVideoDecodeAccelerator
   // Reset token for the DX11 device manager.
   uint32_t dx11_dev_manager_reset_token_;
 
-  uint32_t dx11_dev_manager_reset_token_format_conversion_;
-
   // The EGL config to use for decoded frames.
   EGLConfig egl_config_;