Make content_shell link in the GN build.

content/renderer/pepper/video_decoder_shim.cc

Index: content/renderer/pepper/video_decoder_shim.cc
diff --git a/content/renderer/pepper/video_decoder_shim.cc b/content/renderer/pepper/video_decoder_shim.cc
index 0344cc4fcde0ce1c902e1ab872c1251e829e2961..c52c285a10291e218bf3db516f915aa50fc8244e 100644
--- a/content/renderer/pepper/video_decoder_shim.cc
+++ b/content/renderer/pepper/video_decoder_shim.cc
@@ -125,10 +125,13 @@ VideoDecoderShim::DecoderImpl::~DecoderImpl() {
 void VideoDecoderShim::DecoderImpl::Initialize(
     media::VideoDecoderConfig config) {
   DCHECK(!decoder_);
+#if !defined(MEDIA_DISABLE_LIBVPX)
   if (config.codec() == media::kCodecVP9) {
     decoder_.reset(
         new media::VpxVideoDecoder(base::MessageLoopProxy::current()));
-  } else {
+  } else
+#endif
+  {
     scoped_ptr<media::FFmpegVideoDecoder> ffmpeg_video_decoder(
         new media::FFmpegVideoDecoder(base::MessageLoopProxy::current()));
     ffmpeg_video_decoder->set_decode_nalus(true);