About New audio html5 tags and CSS

Dear W3C,

Excuse me if my english isn't perfect. I will try to explain to you my 
problem with audio tags and CSS:

*html tags*

1 - With Google Chrome Version 64 if you don't put the tag 
*controlsList="nodownload"*  a button to download is present on the 
audio control. But the W3C checker find that it is a mistake. Why ?

2 - On Safari, you can let a volume between 0 and 1 for exemple 
*volume="0.8"* as audio tag. It doesn't work for other browsers. W3C 
checker find that it is a mistake.

*
*

*CSS*

In *Mozilla* with the CSS code:

      audio {
         height: 15px;
         width: 110px;
         border-radius: 46%;
         box-shadow: 5px 2px 10px #252421;
         color: rgb(250, 251, 228);
         background-color: rgba(0, 2, 0, 0.9);
     }
I have a beautiful eliptique control, but in Chrome a white rectangle 
cover the audio and we only guess the eliptique shadow.

In *Chrome* with the CSS code:
     audio, audio::-webkit-media-controls-panel {
         height: 15px;
         width: 110px;
         border-radius: 46%;
         color: rgb(250, 251, 228);
         background-color: rgba(0, 2, 0, 0.9);
     }
I have also a beautiful eliptique control. Note that if I don't put 
audio it make a rectangle background with a shadow. But in Mozilla I 
have the default control.

What I can't understand is that if I make this CSS code:
/Ce que je ne comprends pas est que si 'on code en CSS:/

     audio, audio::-webkit-media-controls-panel, 
audio::-moz-media-controls-panel {
         height: 15px;
         width: 110px;
         border-radius: 46%;
         color: rgb(250, 251, 228);
         background-color: rgba(0, 2, 0, 0.9);
     }/
//Cela marche dans Mozilla et pas dans Chrome. Comment faire pour que 
cela marche dans tous les navigateurs ?/
It works only in Mozilla but not in Chrome. How can I do to make it 
works in all the new browsers ?
If you are not concerned can you transmiss thoses problems to the good 
instance of W3C ? Thank you.

Best regards

Bien cordialement

Jeanne

/_☺ Sauvons les arbres et le papier. N'imprimons que si nécessaire. ☺ /