Add libvpx wrapper to media to support VP9 video decoding.

net/base/mime_util.cc

Index: net/base/mime_util.cc
diff --git a/net/base/mime_util.cc b/net/base/mime_util.cc
index 262b400e327270a6211be50fa9acc695e33bd960..51b08bce21efc713c1d890cc841af06ca6d2b9b7 100644
--- a/net/base/mime_util.cc
+++ b/net/base/mime_util.cc
@@ -310,6 +310,7 @@ static const char* const common_media_codecs[] = {
   "vorbis",
   "opus",
   "vp8",
+  "vp9",
   "1"  // WAVE_FORMAT_PCM.
 };
 
@@ -422,7 +423,7 @@ struct MediaFormatStrict {
 };
 
 static const MediaFormatStrict format_codec_mappings[] = {
-  { "video/webm", "vorbis,opus,vp8,vp8.0" },
+  { "video/webm", "vorbis,opus,vp8,vp8.0,vp9,vp9.0" },
   { "audio/webm", "vorbis,opus" },
   { "audio/wav", "1" }
 };