RFR: 8281631: HashMap copy constructor and putAll can over-allocate table [v19]

[XenoAmess]

> 8281631: HashMap copy constructor and putAll can over-allocate table

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

 - migrate to junit
 - change threshold

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Changes:
  - all: https://git.openjdk.java.net/jdk/pull/7431/files
  - new: https://git.openjdk.java.net/jdk/pull/7431/files/cdfb03bb..aa599698

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=7431&range=18
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=7431&range=17-18

  Stats: 64 lines in 2 files changed: 17 ins; 17 del; 30 mod
  Patch: https://git.openjdk.java.net/jdk/pull/7431.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/7431/head:pull/7431

PR: https://git.openjdk.java.net/jdk/pull/7431