RFR: 8274699: Certain blend modes cannot be set from CSS [v2]

[Marius Hanl]

> This PR fixes a bug where the blend mode will be falsely recognized as a color and therefore won't be set. 
> Also a ClassCastException is thrown (The converter expects a String, but gets a Color).
> 
> Note: There is another similar bug but I can't reproduce it (Tried with 18-ea+3).
> https://bugs.openjdk.java.net/browse/JDK-8268657
> It also looks different so I don't think this PR fixes this, if it is still there.

Marius Hanl has updated the pull request incrementally with two additional commits since the last revision:

 - 8274699: Revert whitespace
 - 8274699: Revert minor code change

-------------

Changes:
  - all: https://git.openjdk.java.net/jfx/pull/640/files
  - new: https://git.openjdk.java.net/jfx/pull/640/files/2a18bf24..302b6425

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jfx&pr=640&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jfx&pr=640&range=00-01

  Stats: 9 lines in 1 file changed: 5 ins; 0 del; 4 mod
  Patch: https://git.openjdk.java.net/jfx/pull/640.diff
  Fetch: git fetch https://git.openjdk.java.net/jfx pull/640/head:pull/640

PR: https://git.openjdk.java.net/jfx/pull/640