Fix ShapeResult::offsetForPosition for RTL scripts

Fix ShapeResult::offsetForPosition for RTL scripts

CachingWordShapeIterator splits runs in the logical order, but
ShapeResult::offsetForPosition() expected the input to be in the visual
order.

This patch fixes ShapeResult::offsetForPosition() to handle the list
of ShapeResult from CachingWordShapeIterator in the logical order.

This is a regression of "Change Font::offsetForPositionForComplexText
to use CachingWordShapeIterator"[1]. Unfortunately tests in the CL did
not catch this logic/visual inconsistency. The test was updated to
include it.

The test string has a diacritic mark at offset 1, and the test ensures
offsetForPosition() dose not return 1. All platforms pass this criteria,
however, only Mac test runner does not return offset 5 (Mac content
shell is fine) so Mac -expeted is added separately.

[1] https://codereview.chromium.org/1248453004/

BUG=518347
TEST=editing/selection/offset-from-point-complex-scripts.html

Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=201181

[kojii, 2015-08-25 12:48:37]

kojii@chromium.org changed reviewers:
+ drott@chromium.org, eae@chromium.org

[kojii, 2015-08-25 12:48:37]

PTAL.

Mac test runner not returning 5 is still a mystery to me, but my take is that
it's not too important to figure out since content shell is working fine. Please
let me know if you disagree.

[eae, 2015-08-25 16:49:25]

LGTM

[kojii, 2015-08-26 01:07:13]

The CQ bit was checked by kojii@chromium.org

[commit-bot: I haz the power, 2015-08-26 01:07:35]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1314543003/100001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1314543003/100001

[commit-bot: I haz the power, 2015-08-26 01:12:53]

Committed patchset #6 (id:100001) as
https://src.chromium.org/viewvc/blink?view=rev&revision=201181