RFR: 8272808: Update constant collections to use the new immutable collections - leftovers

[Nir Lisker]

Replacements of more immutable collections.

One thing I found was that the field `idMap` in `com.sun.java.scene.web.WebViewHelper.WebView` seems unused. I can remove it if that's indeed the case.

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

Commit messages:
 - Fix a previous change
 - More leftovers
 - Unified style
 - Fix mistake from previous commit
 - Replace map in JSCL
 - Initial commit of 2 files

Changes: https://git.openjdk.java.net/jfx/pull/627/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jfx&pr=627&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8272808
  Stats: 162 lines in 7 files changed: 0 ins; 28 del; 134 mod
  Patch: https://git.openjdk.java.net/jfx/pull/627.diff
  Fetch: git fetch https://git.openjdk.java.net/jfx pull/627/head:pull/627

PR: https://git.openjdk.java.net/jfx/pull/627