Implement |pic_order_cnt| computation for VTVideoDecode accelerator.

content/common/gpu/media/vt_video_decode_accelerator.h

Index: content/common/gpu/media/vt_video_decode_accelerator.h
diff --git a/content/common/gpu/media/vt_video_decode_accelerator.h b/content/common/gpu/media/vt_video_decode_accelerator.h
index 2a08421b51b1d5eca59c795662352958e8588d46..10dc319e895120983872b286603d41087827dd4c 100644
--- a/content/common/gpu/media/vt_video_decode_accelerator.h
+++ b/content/common/gpu/media/vt_video_decode_accelerator.h
@@ -16,7 +16,7 @@
 #include "base/message_loop/message_loop.h"
 #include "base/threading/thread.h"
 #include "base/threading/thread_checker.h"
-#include "content/common/gpu/media/h264_dpb.h"
+#include "content/common/gpu/media/h264_poc.h"
 #include "content/common/gpu/media/vt.h"
 #include "media/filters/h264_parser.h"
 #include "media/video/video_decode_accelerator.h"
@@ -77,9 +77,12 @@ class VTVideoDecodeAccelerator : public media::VideoDecodeAccelerator {
     int32_t bitstream_id;
 
     // Relative presentation order of this frame (see AVC spec).
-    // TODO(sandersd): Reorder window size.
     int32_t pic_order_cnt;
 
+    // Nnumber of frames after this one in decode order that can appear before
+    // before it in presentation order.
+    int32_t reorder_window;
+
     // Size of the decoded frame.
     // TODO(sandersd): visible_rect.
     gfx::Size coded_size;
@@ -100,6 +103,13 @@ class VTVideoDecodeAccelerator : public media::VideoDecodeAccelerator {
   // Methods for interacting with VideoToolbox. Run on |decoder_thread_|.
   //
 
+  // Compute the |pic_order_cnt| for a frame. Returns true or calls
+  // NotifyError() before returning false.
+  bool ComputePicOrderCnt(
+      const media::H264SPS* sps,
+      const media::H264SliceHeader& slice_hdr,
+      Frame* frame);
+
   // Set up VideoToolbox using the current SPS and PPS. Returns true or calls
   // NotifyError() before returning false.
   bool ConfigureDecoder();
@@ -198,6 +208,7 @@ class VTVideoDecodeAccelerator : public media::VideoDecodeAccelerator {
   std::vector<uint8_t> last_spsext_;
   int last_pps_id_;
   std::vector<uint8_t> last_pps_;
+  H264POC poc_;
 
   //
   // Shared state (set up and torn down on GPU thread).