RFR: 8295323: Unnecessary HashTable usage in StyleSheet [v2]

[Andrey Turbanov]

> Hashtable was used only from single thread. And only non-null key/values added to it. We can safely replace it with HashSet.

Andrey Turbanov has updated the pull request incrementally with one additional commit since the last revision:

  8295323: Unnecessary HashTable usage in StyleSheet
  
  rename tempHashSet to alreadyChecked

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Changes:
  - all: https://git.openjdk.org/jdk/pull/10522/files
  - new: https://git.openjdk.org/jdk/pull/10522/files/ee8cbfd5..f89a85c4

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=10522&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=10522&range=00-01

  Stats: 6 lines in 1 file changed: 0 ins; 0 del; 6 mod
  Patch: https://git.openjdk.org/jdk/pull/10522.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/10522/head:pull/10522

PR: https://git.openjdk.org/jdk/pull/10522