RFR: 8303217: Webview loaded webpage is not showing play, volume related buttons for embeded Audio/Video elements [v4]

[Jay Bhaskar]

> Issue: default html5 video element not showing media controls
> Details: Media control design has been refactored in the current Webkit Gtk port. The CSS id 
>                 and properties related to media buttons, and slider have been removed, due to which the 
>                 media style mediaControlsAdwaita.css values are not being applied.
> Solution: restored media control keywords and mapped to CSS keywords values.

Jay Bhaskar has refreshed the contents of this pull request, and previous commits have been removed. The incremental views will show differences compared to the previous content of the PR. The pull request contains one new commit since the last revision:

  Handle missing enuns in CSSPrimitiveValueMappings.h

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Changes:
  - all: https://git.openjdk.org/jfx/pull/1049/files
  - new: https://git.openjdk.org/jfx/pull/1049/files/adf1f1be..ca622c2e

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jfx&pr=1049&range=03
 - incr: https://webrevs.openjdk.org/?repo=jfx&pr=1049&range=02-03

  Stats: 0 lines in 0 files changed: 0 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jfx/pull/1049.diff
  Fetch: git fetch https://git.openjdk.org/jfx pull/1049/head:pull/1049

PR: https://git.openjdk.org/jfx/pull/1049