[OS X] Upright vertical text is completely broken for multi-code-unit codepoints

[OS X] Upright vertical text is completely broken for multi-code-unit codepoints
https://bugs.webkit.org/show_bug.cgi?id=138891

Reviewed by Dan Bernstein.

Source/WebCore:

We were assuming that we can use the string index (in UTF-16) as the glyph
index. This falls down when a single codepoint (and glyph) contians
multiple code units.

Test: platform/mac/fast/text/multiple-codeunit-vertical-upright.html

* platform/graphics/GlyphPage.h:
* platform/graphics/mac/GlyphPageTreeNodeMac.cpp:
(WebCore::GlyphPage::fill):

LayoutTests:

Make sure a single upright vertical multi-code-unit codepoint is rendered the same as
the same codepoint rendered horizontally.

* platform/mac/fast/text/multiple-codeunit-vertical-upright-expected.html: Added.
* platform/mac/fast/text/multiple-codeunit-vertical-upright.html: Added.
* platform/mac/fast/text/resources/multiple-codeunit-vertical-upright.otf: Added.

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@176372 268f45cc-cd09-0410-ab3c-d52691b4dbfc