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..8c33d6cb66a4455c0f0ac8dec96245b7db3f7efe 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"
@@ -367,11 +368,14 @@ bool VpxVideoDecoder::VpxDecode(const scoped_refptr<DecoderBuffer>& buffer,
   // Pass |buffer| to libvpx.
   int64 timestamp = buffer->timestamp().InMicroseconds();
   void* user_priv = reinterpret_cast<void*>(&timestamp);
+
+  TRACE_EVENT_BEGIN1("video", "vpx_codec_decode", "timestamp", timestamp);

[DaleCurtis, 2014/12/03 19:12:16]

You can just use TRACE_EVENT_1() and scope it around this call with {} to avoid
the begin/end business. 

[Tom Finegan, 2014/12/03 19:33:09]

I thought the extra scoping was uglier. :)

Done.

   vpx_codec_err_t status = vpx_codec_decode(vpx_codec_,
                                             buffer->data(),
                                             buffer->data_size(),
                                             user_priv,
                                             0);
+  TRACE_EVENT_END1("video", "vpx_codec_decode", "timestamp", timestamp);
   if (status != VPX_CODEC_OK) {
     LOG(ERROR) << "vpx_codec_decode() failed, status=" << status;
     return false;
@@ -400,11 +404,15 @@ 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_BEGIN1("video", "vpx_codec_decode_alpha",

[DaleCurtis, 2014/12/03 19:12:16]

Ditto.

+                         "timestamp_alpha", timestamp_alpha);
       status = vpx_codec_decode(vpx_codec_alpha_,
                                 buffer->side_data() + 8,
                                 buffer->side_data_size() - 8,
                                 user_priv_alpha,
                                 0);
+      TRACE_EVENT_END1("video", "vpx_codec_decode_alpha",
+                       "timestamp_alpha", timestamp_alpha);
 
       if (status != VPX_CODEC_OK) {
         LOG(ERROR) << "vpx_codec_decode() failed on alpha, status=" << status;