Arabic shaping is incorrect if ZWNJ exist

Arabic shaping is incorrect if ZWNJ exist
https://bugs.webkit.org/show_bug.cgi?id=89843

Reviewed by Dan Bernstein.

Source/WebCore:

mac port treats ZWJ (zero-width-joiner) and ZWNJ (zero-width-non-joiner) as a part of combining
character sequence. This could cause a problem when the font doesn't have glyph mapping of ZWJ and ZWNJ.
Suppose the text to be rendered is "U+0645(MEEM) U+06CC(FARSI YEH) U+200C(ZWNJ)". In this case, U+0645
and U+06CC are rendered in isolated form if the font doesn't have a glyph for ZWNJ. They should be joined.

This patch changes handling of ZWJ and ZWNJ. Treats ZWJ and ZWNJ as base characters so that a complex text
run isn't separate at the point of ZWJ and ZWNJ even the font doesn't contain glyphs for them.
If ComplexTextController finds ZWJ, it doesn't split the current complex text run.

Test: platform/mac/fast/text/arabic-zwj-and-zwnj.html

* platform/graphics/mac/ComplexTextController.cpp:
(WebCore::advanceByCombiningCharacterSequence): Don't treat ZWJ and ZWNJ as a part of combining character sequence.
(WebCore::ComplexTextController::collectComplexTextRuns): Set fontData to nextFontData if the baseCharacter is ZWJ.

LayoutTests:

* platform/mac/fast/text/arabic-zwj-and-zwnj-expected.html: Added.
* platform/mac/fast/text/arabic-zwj-and-zwnj.html: Added.

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@121643 268f45cc-cd09-0410-ab3c-d52691b4dbfc