RFR: 8260257: [Linux] WebView no longer reacts to some mouse events

[Arun Joseph]

Timer in RunLoopGeneric has an open bug in WebKit (https://bugs.webkit.org/show_bug.cgi?id=189335) causing the timer to remain active even after firing.

Reverting back to WebCore Timer for ScrollAnimation in Linux.

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Commit messages:
 - 8260257: [Linux] WebView no longer reacts to some mouse events

Changes: https://git.openjdk.java.net/jfx/pull/404/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jfx&pr=404&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8260257
  Stats: 8 lines in 2 files changed: 8 ins; 0 del; 0 mod
  Patch: https://git.openjdk.java.net/jfx/pull/404.diff
  Fetch: git fetch https://git.openjdk.java.net/jfx pull/404/head:pull/404

PR: https://git.openjdk.java.net/jfx/pull/404