According to that commitment Chrome version of Android is able to extract HDR VP9 metadata from the video container and submit it to MediaCodec. In layman terms it means Chrome will be able to play HDR video on compatible devices.
In addition to the information, High Dynamic Range (HDR) video offers superior color contrast and accuracy resulting in overall video quality improvement. A number of leading smartphone like Samsung Galaxy S8, Note 8, LG V30, Sony Xperia XZ Premium and other HDR screen supported.
Apps like YouTube, Google Play Movies, and Netflix have supported HDR video, but the amount of HDR content is currently limited. So support for HDR video will still be popping up in the future.