Set |use_prev_in_find_mv_refs| correctly.

At least, set it correctly for some value of "correct".

Bug: 1091466
Change-Id: Ib5f242fcc923333d647e5209233b718acf902197
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2232777Reviewed-by: Ted Meyer <tmathmeyer@chromium.org>
Commit-Queue: Frank Liberato <liberato@chromium.org>
Cr-Commit-Position: refs/heads/master@{#776174}

media/gpu/windows/d3d11_vp9_accelerator.cc

@@ -101,7 +101,6 @@ void D3D11VP9Accelerator::CopyFrameParams(const D3D11VP9Picture& pic,
   COPY_PARAM(frame_context_idx);
   COPY_PARAM(reset_frame_context);
   COPY_PARAM(allow_high_precision_mv);
-  COPY_PARAM(refresh_frame_context);
   COPY_PARAM(frame_parallel_decoding_mode);
   COPY_PARAM(intra_only);
   COPY_PARAM(frame_context_idx);
@@ -125,6 +124,18 @@ void D3D11VP9Accelerator::CopyFrameParams(const D3D11VP9Picture& pic,
   SET_PARAM(log2_tile_rows, tile_rows_log2);
 #undef COPY_PARAM
 #undef SET_PARAM
+
+  // This is taken, approximately, from libvpx.
+  gfx::Size this_frame_size(pic.frame_hdr->frame_width,
+                            pic.frame_hdr->frame_height);
+  pic_params->use_prev_in_find_mv_refs = last_frame_size_ == this_frame_size &&
+                                         !pic.frame_hdr->error_resilient_mode &&
+                                         !pic.frame_hdr->intra_only &&
+                                         last_show_frame_;
+
+  // TODO(liberato): So, uh, do we ever need to reset this?
+  last_frame_size_ = this_frame_size;
+  last_show_frame_ = pic.frame_hdr->show_frame;
 }
 
 void D3D11VP9Accelerator::CopyReferenceFrames(

media/gpu/windows/d3d11_vp9_accelerator.h

@@ -76,6 +76,10 @@ class D3D11VP9Accelerator : public VP9Decoder::VP9Accelerator {
   ComD3D11VideoDevice video_device_;
   std::unique_ptr<VideoContextWrapper> video_context_;
 
+  // Used to set |use_prev_in_find_mv_refs| properly.
+  gfx::Size last_frame_size_;
+  bool last_show_frame_ = false;
+
   DISALLOW_COPY_AND_ASSIGN(D3D11VP9Accelerator);
 };