V4L2SVDA: Add a VP9Accelerator implementation utilizing the V4L2 VP9 frame API.

Add an implementation of VP9Accelerator to V4L2SliceVideoDecodeAccelerator,
using the new V4L2 VP9 frame API.

Also slightly reorganize context handling and update callbacks
in Vp9Decoder and Vp9Parser.

TEST=vdatest, crosvideo.appspot
BUG=chrome-os-partner:56703

Review-Url: https://codereview.chromium.org/2229353002
Cr-Commit-Position: refs/heads/master@{#414961}

diff --git a/media/gpu/vp9_decoder.cc b/media/gpu/vp9_decoder.cc
index 993a8a1..a6f40d9e 100644
--- a/media/gpu/vp9_decoder.cc
+++ b/media/gpu/vp9_decoder.cc

@@ -6,6 +6,7 @@
 
 #include <memory>
 
+#include "base/bind.h"
 #include "base/logging.h"
 #include "media/base/limits.h"
 #include "media/gpu/vp9_decoder.h"
@@ -17,8 +18,9 @@
 VP9Decoder::VP9Accelerator::~VP9Accelerator() {}
 
 VP9Decoder::VP9Decoder(VP9Accelerator* accelerator)
-    : state_(kNeedStreamMetadata), parser_(false), accelerator_(accelerator) {
-  DCHECK(accelerator_);
+    : state_(kNeedStreamMetadata),
+      accelerator_(accelerator),
+      parser_(accelerator->IsFrameContextRequired()) {
   ref_frames_.resize(kVp9NumRefFrames);
 }
 
@@ -54,7 +56,7 @@
     // Read a new frame header if one is not awaiting decoding already.
     if (!curr_frame_hdr_) {
       std::unique_ptr<Vp9FrameHeader> hdr(new Vp9FrameHeader());
-      Vp9Parser::Result res = parser_.ParseNextFrame(hdr.get(), nullptr);
+      Vp9Parser::Result res = parser_.ParseNextFrame(hdr.get());
       switch (res) {
         case Vp9Parser::kOk:
           curr_frame_hdr_.reset(hdr.release());
@@ -69,7 +71,8 @@
           return kDecodeError;
 
         case Vp9Parser::kAwaitingRefresh:
-          NOTREACHED();
+          DVLOG(4) << "Awaiting context update";
+          return kNeedContextUpdate;
       }
     }
 
@@ -152,12 +155,35 @@
   }
 }
 
+void VP9Decoder::UpdateFrameContext(
+    const scoped_refptr<VP9Picture>& pic,
+    const base::Callback<void(const Vp9FrameContext&)>& context_refresh_cb) {
+  DCHECK(!context_refresh_cb.is_null());
+  Vp9FrameContext frame_ctx;
+  memset(&frame_ctx, 0, sizeof(frame_ctx));
+
+  if (!accelerator_->GetFrameContext(pic, &frame_ctx)) {
+    SetError();
+    return;
+  }
+
+  context_refresh_cb.Run(frame_ctx);
+}
+
 bool VP9Decoder::DecodeAndOutputPicture(scoped_refptr<VP9Picture> pic) {
   DCHECK(!pic_size_.IsEmpty());
   DCHECK(pic->frame_hdr);
 
-  if (!accelerator_->SubmitDecode(pic, parser_.GetSegmentation(),
-                                  parser_.GetLoopFilter(), ref_frames_))
+  base::Closure done_cb;
+  const auto& context_refresh_cb =
+      parser_.GetContextRefreshCb(pic->frame_hdr->frame_context_idx);
+  if (!context_refresh_cb.is_null())
+    done_cb = base::Bind(&VP9Decoder::UpdateFrameContext,
+                         base::Unretained(this), pic, context_refresh_cb);
+
+  const Vp9Parser::Context& context = parser_.context();
+  if (!accelerator_->SubmitDecode(pic, context.segmentation(),
+                                  context.loop_filter(), ref_frames_, done_cb))
     return false;
 
   if (pic->frame_hdr->show_frame) {