VpxVideoDecoder: add buffer size to TRACE_EVENT

This CL adds |buffer->data_size()| to the decode TRACE_EVENT()
in vpx_video_decoder.cc.

The addition helps correlating the time it takes to decode with
the encoded buffer size; examples of how it looks like:

https://i.imgur.com/LUXijLO.png (https://imgur.com/a/1Gllg)
 or
https://i.imgur.com/67QfgKj.png (https://imgur.com/a/3PhQt)


Cq-Include-Trybots: master.tryserver.chromium.android:android_optional_gpu_tests_rel;master.tryserver.chromium.linux:linux_optional_gpu_tests_rel;master.tryserver.chromium.mac:mac_optional_gpu_tests_rel;master.tryserver.chromium.win:win_optional_gpu_tests_rel
Change-Id: I240b6f49d61fa385045e3a67fb4fc1e6e4c96fe0
Reviewed-on: https://chromium-review.googlesource.com/812160Reviewed-by: Dan Sanders <sandersd@chromium.org>
Commit-Queue: Miguel Casas <mcasas@chromium.org>
Cr-Commit-Position: refs/heads/master@{#522272}

media/filters/vpx_video_decoder.cc

@@ -320,7 +320,8 @@ bool VpxVideoDecoder::VpxDecode(const DecoderBuffer* buffer,
   int64_t timestamp = buffer->timestamp().InMicroseconds();
   void* user_priv = reinterpret_cast<void*>(&timestamp);
   {
-    TRACE_EVENT1("media", "vpx_codec_decode", "timestamp", timestamp);
+    TRACE_EVENT2("media", "vpx_codec_decode", "timestamp", timestamp,
+                 "buffer size (B)", buffer->data_size());
     vpx_codec_err_t status =
         vpx_codec_decode(vpx_codec_.get(), buffer->data(), buffer->data_size(),
                          user_priv, 0 /* deadline */);