RFR: JDK-8307083: Open source some drag and drop tests 3 [v3]

[Alisen Chung]

> moving tests to open

Alisen Chung has updated the pull request incrementally with two additional commits since the last revision:

 - Merge branch 'JTREG_TEST_SPRINT3' of github.com:alisenchung/jdk into JTREG_TEST_SPRINT3
 - moved check onto EDT

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Changes:
  - all: https://git.openjdk.org/jdk/pull/13764/files
  - new: https://git.openjdk.org/jdk/pull/13764/files/b99982a8..de4cfd7d

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=13764&range=02
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=13764&range=01-02

  Stats: 5 lines in 1 file changed: 2 ins; 0 del; 3 mod
  Patch: https://git.openjdk.org/jdk/pull/13764.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/13764/head:pull/13764

PR: https://git.openjdk.org/jdk/pull/13764