RFR: 7083187: Class CSS.CssValue is missing implementations of equals() and hashCode() [v8]

[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 one additional commit since the last revision:

  Test and fix updated as per review comments

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Changes:
  - all: https://git.openjdk.org/jdk/pull/13405/files
  - new: https://git.openjdk.org/jdk/pull/13405/files/717d1a1d..88841b82

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=13405&range=07
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=13405&range=06-07

  Stats: 184 lines in 2 files changed: 68 ins; 71 del; 45 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