Fix for <rdar://problem/4875433> WebView underlines are too thick 
        when scaled small

        When we have a small scale factor, we should follow the line-
        drawing code as if we were printing. Meaning, specifically, that we 
        should not round to device pixels and we should antialias.

        * platform/graphics/cg/GraphicsContextCG.cpp:
        (WebCore::GraphicsContext::drawLineForText):


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@20764 268f45cc-cd09-0410-ab3c-d52691b4dbfc