media: Add tracing around VPx decoding.

media/filters/vpx_video_decoder.cc

Index: media/filters/vpx_video_decoder.cc
diff --git a/media/filters/vpx_video_decoder.cc b/media/filters/vpx_video_decoder.cc
index bf7cc3cdaac32a2c1aa49c5f8d00d362a051ab9b..ffbbcd910eea60216351c3180791a44ef9df3a65 100644
--- a/media/filters/vpx_video_decoder.cc
+++ b/media/filters/vpx_video_decoder.cc
@@ -11,6 +11,7 @@
 #include "base/bind.h"
 #include "base/callback_helpers.h"
 #include "base/command_line.h"
+#include "base/debug/trace_event.h"
 #include "base/location.h"
 #include "base/logging.h"
 #include "base/single_thread_task_runner.h"
@@ -361,17 +362,21 @@ void VpxVideoDecoder::DecodeBuffer(const scoped_refptr<DecoderBuffer>& buffer) {
 
 bool VpxVideoDecoder::VpxDecode(const scoped_refptr<DecoderBuffer>& buffer,
                                 scoped_refptr<VideoFrame>* video_frame) {
+  TRACE_EVENT0("video", "VpxDecode");

[fgalligan1, 2014/12/03 18:29:56]

Is this needed?

[Tom Finegan, 2014/12/03 18:51:39]

This tracked the entire VpxDecode() call. Removed.

   DCHECK(video_frame);
   DCHECK(!buffer->end_of_stream());
 
   // Pass |buffer| to libvpx.
   int64 timestamp = buffer->timestamp().InMicroseconds();
   void* user_priv = reinterpret_cast<void*>(&timestamp);
+
+  TRACE_EVENT_BEGIN0("video", "vpx_codec_decode");

[fgalligan1, 2014/12/03 18:29:56]

Maybe add the timestamp so we could distinguish the decode calls in the trace?

[Tom Finegan, 2014/12/03 18:51:39]

Done.

   vpx_codec_err_t status = vpx_codec_decode(vpx_codec_,
                                             buffer->data(),
                                             buffer->data_size(),
                                             user_priv,
                                             0);
+  TRACE_EVENT_END0("video", "vpx_codec_decode");
   if (status != VPX_CODEC_OK) {
     LOG(ERROR) << "vpx_codec_decode() failed, status=" << status;
     return false;
@@ -379,7 +384,9 @@ bool VpxVideoDecoder::VpxDecode(const scoped_refptr<DecoderBuffer>& buffer,
 
   // Gets pointer to decoded data.
   vpx_codec_iter_t iter = NULL;
+  TRACE_EVENT_BEGIN0("video", "vpx_codec_get_frame");

[fgalligan1, 2014/12/03 18:29:56]

I think we can get rid of these. They should pretty much just return a pointer
at this point.

[Tom Finegan, 2014/12/03 18:51:39]

Done.

   const vpx_image_t* vpx_image = vpx_codec_get_frame(vpx_codec_, &iter);
+  TRACE_EVENT_END0("video", "vpx_codec_get_frame");
   if (!vpx_image) {
     *video_frame = NULL;
     return true;
@@ -400,11 +407,13 @@ bool VpxVideoDecoder::VpxDecode(const scoped_refptr<DecoderBuffer>& buffer,
     const uint64 side_data_id = base::NetToHost64(
         *(reinterpret_cast<const uint64*>(buffer->side_data())));
     if (side_data_id == 1) {
+      TRACE_EVENT_BEGIN0("video", "vpx_codec_decode_alpha");
       status = vpx_codec_decode(vpx_codec_alpha_,
                                 buffer->side_data() + 8,
                                 buffer->side_data_size() - 8,
                                 user_priv_alpha,
                                 0);
+      TRACE_EVENT_END0("video", "vpx_codec_decode_alpha");
 
       if (status != VPX_CODEC_OK) {
         LOG(ERROR) << "vpx_codec_decode() failed on alpha, status=" << status;
@@ -413,7 +422,9 @@ bool VpxVideoDecoder::VpxDecode(const scoped_refptr<DecoderBuffer>& buffer,
 
       // Gets pointer to decoded data.
       vpx_codec_iter_t iter_alpha = NULL;
+      TRACE_EVENT_BEGIN0("video", "vpx_codec_get_frame_alpha");
       vpx_image_alpha = vpx_codec_get_frame(vpx_codec_alpha_, &iter_alpha);
+      TRACE_EVENT_END0("video", "vpx_codec_get_frame_alpha");
       if (!vpx_image_alpha) {
         *video_frame = NULL;
         return true;