color: Clarify default behaviors

media/filters/ffmpeg_video_decoder.cc

Index: media/filters/ffmpeg_video_decoder.cc
diff --git a/media/filters/ffmpeg_video_decoder.cc b/media/filters/ffmpeg_video_decoder.cc
index c9b3b3060b4096c7b59b4da11e499c35e9fb0ee4..ea89e77f2b60527376ccf9a0629e26e33682f3da 100644
--- a/media/filters/ffmpeg_video_decoder.cc
+++ b/media/filters/ffmpeg_video_decoder.cc
@@ -185,12 +185,13 @@ int FFmpegVideoDecoder::GetVideoBuffer(struct AVCodecContext* codec_context,
   if (codec_context->color_primaries != AVCOL_PRI_UNSPECIFIED ||
       codec_context->color_trc != AVCOL_TRC_UNSPECIFIED ||
       codec_context->colorspace != AVCOL_SPC_UNSPECIFIED) {
-    video_frame->set_color_space(
-        gfx::ColorSpace(codec_context->color_primaries,
-                        codec_context->color_trc, codec_context->colorspace,
-                        codec_context->color_range != AVCOL_RANGE_MPEG
-                            ? gfx::ColorSpace::RangeID::FULL
-                            : gfx::ColorSpace::RangeID::LIMITED));
+    video_frame->set_color_space(gfx::ColorSpace(
+        gfx::ColorSpace::PrimaryIDFromH264(codec_context->color_primaries),
+        gfx::ColorSpace::TransferIDFromH264(codec_context->color_trc),
+        gfx::ColorSpace::MatrixIDFromH264(codec_context->colorspace),
+        codec_context->color_range != AVCOL_RANGE_MPEG
+            ? gfx::ColorSpace::RangeID::FULL
+            : gfx::ColorSpace::RangeID::LIMITED));
   }
 
   for (size_t i = 0; i < VideoFrame::NumPlanes(video_frame->format()); i++) {