RFR: 8301022: Video distortion is observed while playing youtube video

[Jay Bhaskar]

Issue: current update is breaking the rendering of media controls on youtube video playback
           For the Webkit Gtk platform, the layout class name is returned as AdwaitaLayoutTraits
           which is incompatible with the JAVA platform.
Solution: Use mediaControlsAdwaitaJavaScript and mediaControlsAdwaitaUserAgentStyleSheet
                which is compatible with RenderThemeJava. 
Test: After the fix, open youtube.com and play any video, mouse hover on the video area, control should come up.
         Without the fix, open youtube.com and play any video, mouse hover on the video area, and the control 
          should come up overlapping with each other.

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Commit messages:
 - 8301022: Video distortion is observed while playing youtube video

Changes: https://git.openjdk.org/jfx/pull/1045/files
 Webrev: https://webrevs.openjdk.org/?repo=jfx&pr=1045&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8301022
  Stats: 1531 lines in 4 files changed: 1531 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jfx/pull/1045.diff
  Fetch: git fetch https://git.openjdk.org/jfx pull/1045/head:pull/1045

PR: https://git.openjdk.org/jfx/pull/1045