color: Clarify default behaviors

media/filters/h264_parser.cc

Index: media/filters/h264_parser.cc
diff --git a/media/filters/h264_parser.cc b/media/filters/h264_parser.cc
index 052f441d258bc77a38f9e313ceb84bcffd5e584c..ef4b573760c60096279910e354aac9ec289eae24 100644
--- a/media/filters/h264_parser.cc
+++ b/media/filters/h264_parser.cc
@@ -126,16 +126,17 @@ base::Optional<gfx::Rect> H264SPS::GetVisibleRect() const {
 gfx::ColorSpace H264SPS::GetColorSpace() const {
   if (colour_description_present_flag) {
     return gfx::ColorSpace(
-        colour_primaries, transfer_characteristics, matrix_coefficients,
+        gfx::ColorSpace::PrimaryIDFromH264(colour_primaries),
+        gfx::ColorSpace::TransferIDFromH264(transfer_characteristics),
+        gfx::ColorSpace::MatrixIDFromH264(matrix_coefficients),
         video_full_range_flag ? gfx::ColorSpace::RangeID::FULL
                               : gfx::ColorSpace::RangeID::LIMITED);
   } else {
-    return gfx::ColorSpace(gfx::ColorSpace::PrimaryID::UNSPECIFIED,
-                           gfx::ColorSpace::TransferID::UNSPECIFIED,
-                           gfx::ColorSpace::MatrixID::UNSPECIFIED,
-                           video_full_range_flag
-                               ? gfx::ColorSpace::RangeID::FULL
-                               : gfx::ColorSpace::RangeID::LIMITED);
+    return gfx::ColorSpace(
+        gfx::ColorSpace::PrimaryID::BT709, gfx::ColorSpace::TransferID::BT709,
+        gfx::ColorSpace::MatrixID::BT709,
+        video_full_range_flag ? gfx::ColorSpace::RangeID::FULL
+                              : gfx::ColorSpace::RangeID::LIMITED);
   }
 }