RFR: 7083187: Class CSS.CssValue is missing implementations of equals() and hashCode() [v2]

[Prasanta Sadhukhan]

> Two CSS AttributeSet-s can be compared using the AttributeSet.isEqual() method which can fail due to missing implementation of equals method in CSS subclasses.
> In this issue, even when two CSS AttributeSet has same 42 font size string value, Object equality fails.
> Fixed by implementing the equality and hashCode method for CSS.FontSize class.
> 
> All jtreg/jck tests are ok

Prasanta Sadhukhan has updated the pull request incrementally with three additional commits since the last revision:

 - Test fix
 - Test fix
 - Review comment address

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/13405/files
  - new: https://git.openjdk.org/jdk/pull/13405/files/fddecfbb..e24c1405

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=13405&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=13405&range=00-01

  Stats: 187 lines in 3 files changed: 126 ins; 60 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/13405.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/13405/head:pull/13405

PR: https://git.openjdk.org/jdk/pull/13405