media/gpu/VP9Decoder: use std::move() to reduce scoped_refptr duplication.

Bug: 1020668
Test: run vda_tests on kevin

Change-Id: I5679d5ff65159f4f3bcb7dd62f5a3e1e09964739
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1974726
Commit-Queue: Chih-Yu Huang <akahuang@chromium.org>
Reviewed-by: Alexandre Courbot <acourbot@chromium.org>
Reviewed-by: Hirokazu Honda <hiroh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#726369}

media/gpu/vp9_decoder.cc

@@ -253,7 +253,7 @@ VP9Decoder::DecodeResult VP9Decoder::Decode() {
     }
     pic->frame_hdr = std::move(curr_frame_hdr_);
 
-    if (!DecodeAndOutputPicture(pic)) {
+    if (!DecodeAndOutputPicture(std::move(pic))) {
       SetError();
       return kDecodeError;
     }