[OS X] Glyph spacing for system fonts may be incorrect

[OS X] Glyph spacing for system fonts may be incorrect
https://bugs.webkit.org/show_bug.cgi?id=131967

Reviewed by Simon Fraser.

Source/WebCore:
Covered by existing tests.

* platform/graphics/mac/SimpleFontDataMac.mm:
(WebCore::SimpleFontData::platformWidthForGlyph): Update to use CTFontGetAdvancesForGlyphs() for system fonts
(WebCore::hasCustomTracking):

LayoutTests:
Updating test to be more robust.

* fast/forms/search/intrinsic-search-width-with-decoration-border-padding-expected.txt:
* fast/forms/search/intrinsic-search-width-with-decoration-border-padding.html:

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@167679 268f45cc-cd09-0410-ab3c-d52691b4dbfc