Cherry-pick 12430a2. rdar://problem/95968482

    Disallow content property on video element
    https://bugs.webkit.org/show_bug.cgi?id=242855
    rdar://95968482

    Reviewed by Simon Fraser.

    Disallow content property on video element.

    Matches Firefox and Chrome.

    * Source/WebCore/css/html.css:
    (video):

    Canonical link: https://commits.webkit.org/252574@main

Canonical link: https://commits.webkit.org/252432.92@safari-7614.1.25.3-branch

Source/WebCore/css/html.css

@@ -117,6 +117,7 @@ video {
 #if defined(WTF_PLATFORM_IOS_FAMILY) && WTF_PLATFORM_IOS_FAMILY
     -webkit-tap-highlight-color: transparent;
 #endif
+    content: normal !important;
 }
 
 audio {