Make NGInlineCursor::PositionForPointInChild() to call...

Make NGInlineCursor::PositionForPointInChild() to call NGFragmentItem::PositionForPoint() with child local offset

This patch changes |NGInlineCursor::PositionForPointInChild()| to call
|NGFragmentItem::PositionForPoint()| with child local offset instead of offset
in container because |NGFragmentItem::PositionForPoint()| expects local offset
as |NGPaintFragment:: PositionForPointInText()|.


This patch fixes following tests (at least):
- fast/dom/Document/CaretRangeFromPoint/caretRangeFromPoint-in-user-select-none.html
- fast/dom/Document/CaretRangeFromPoint/caretRangeFromPoint-with-before-style.html
- fast/dom/Document/CaretRangeFromPoint/caretRangeFromPoint-with-first-letter-style.html

Failure counts is decreased to 206 from 215.

Bug: 982194
Change-Id: I839e9f480bb98501fb463da0dae6b42b2eb2b0e5
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2038590
Commit-Queue: Kent Tamura <tkent@chromium.org>
Auto-Submit: Yoshifumi Inoue <yosin@chromium.org>
Reviewed-by: Kent Tamura <tkent@chromium.org>
Cr-Commit-Position: refs/heads/master@{#738777}

third_party/blink/renderer/core/layout/ng/inline/ng_inline_cursor.cc

@@ -806,7 +806,8 @@ PositionWithAffinity NGInlineCursor::PositionForPointInChild(
   DCHECK_EQ(&child_item, CurrentItem());
   switch (child_item.Type()) {
     case NGFragmentItem::kText:
-      return child_item.PositionForPointInText(point, *this);
+      return child_item.PositionForPointInText(
+          point - child_item.OffsetInContainerBlock(), *this);
     case NGFragmentItem::kGeneratedText:
       break;
     case NGFragmentItem::kBox: