https://bugs.webkit.org/show_bug.cgi?id=100050

Reviewed by Antti Koivisto.

Source/WebCore:

Always let WidthIterator iterate over an entire TextRun to avoid problems
with pixel rounding or shaping on partial runs.

This fix is necessary for Qt because the complex font-path can not disable
shaping, leading to the complex path painting slighly different from the
fast path, which messes up selection painting.

No change in functionality, no new tests.

* platform/graphics/Font.cpp:
(WebCore::Font::drawText):
(WebCore::Font::drawEmphasisMarks):
(WebCore::Font::selectionRectForText):
(WebCore::Font::offsetForPosition):
* platform/graphics/FontFastPath.cpp:
(WebCore::Font::getGlyphsAndAdvancesForSimpleText):
(WebCore::Font::selectionRectForSimpleText):
(WebCore::Font::offsetForPositionForSimpleText):
* platform/graphics/GlyphBuffer.h:
(WebCore::GlyphBuffer::add):
(GlyphBuffer):
* platform/graphics/WidthIterator.cpp:
(WebCore::WidthIterator::advanceInternal):
* platform/graphics/WidthIterator.h:
(WidthIterator): Removed now unused advanceOneCharacter method.

LayoutTests:

* fast/text/resources/PTS55F-webfont.ttf: Added.
* fast/text/partial-textruns-expected.html: Added.
* fast/text/partial-textruns.html: Added.

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@154384 268f45cc-cd09-0410-ab3c-d52691b4dbfc