RFR: 8336798: DRT test cssrounding.html test for linear layout fails with WebKit 619.1

[Jay Bhaskar]

Issue: CSSRounding.html DRT Test fails due sub pixel layout. The fractional value adds up to 1px extra height.
Solution: The Prefer height calculation should do flooring of fractional values. This is valid for Linear Layout which is a legacy support to most of the browsers.

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Commit messages:
 - 8336798: DRT test cssrounding.html test for linear layout fails with WebKit 619.1
 - 8335548: testCookieEnabled fails with WebKit 619.1

Changes: https://git.openjdk.org/jfx/pull/1514/files
  Webrev: https://webrevs.openjdk.org/?repo=jfx&pr=1514&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8336798
  Stats: 196 lines in 4 files changed: 193 ins; 0 del; 3 mod
  Patch: https://git.openjdk.org/jfx/pull/1514.diff
  Fetch: git fetch https://git.openjdk.org/jfx.git pull/1514/head:pull/1514

PR: https://git.openjdk.org/jfx/pull/1514