RFR: 8277785: ListView scrollTo jumps to wrong location when CellHeight is changed

[Johan Vos]

When the size of a ListCell is changed and a scrollTo method is invoked without having a layout calculation in between, the old (wrong) size is used to calculcate the total estimate. This happens e.g. when the size is changed in the `updateItem` method.
This PR will immediately resize the cell and sets the new value in the cache containing the cellsizes.

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Commit messages:
 - resize cell when getting it from the pile, and recalculate total estimated size

Changes: https://git.openjdk.java.net/jfx/pull/712/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jfx&pr=712&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8277785
  Stats: 63 lines in 2 files changed: 63 ins; 0 del; 0 mod
  Patch: https://git.openjdk.java.net/jfx/pull/712.diff
  Fetch: git fetch https://git.openjdk.java.net/jfx pull/712/head:pull/712

PR: https://git.openjdk.java.net/jfx/pull/712