RFR: 8306083: Text.hitTest is incorrect when more than one Text node in TextFlow [v8]

[Karthik P K]

> The text run selected in `PrismTextLayout::getHitInfo()` method for character index calculation was not correct when hitTest was invoked for Text node in a TextFlow with more than one Text child. Hence wrong character index value was calculated.
> 
> Since only x, y coordinates were available in the above mentioned method, sending the text as a parameter to this method is necessary so as to know if the text run selected for character index calculation is correct. Along with this change modified the `PrismTextLayout::getHitInfo()` method to calculate the correct character index.
> 
> Added tests to validate the changes.

Karthik P K has updated the pull request incrementally with one additional commit since the last revision:

  Review comments

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

Changes:
  - all: https://git.openjdk.org/jfx/pull/1157/files
  - new: https://git.openjdk.org/jfx/pull/1157/files/1aeb67a9..edb20ec5

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jfx&pr=1157&range=07
 - incr: https://webrevs.openjdk.org/?repo=jfx&pr=1157&range=06-07

  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jfx/pull/1157.diff
  Fetch: git fetch https://git.openjdk.org/jfx.git pull/1157/head:pull/1157

PR: https://git.openjdk.org/jfx/pull/1157