Reviewed by Tony Chang.

        [chromium] Improve spacing support for complex text on Linux

        https://bugs.webkit.org/show_bug.cgi?id=39014

        Previously, our complex text support ignored word-spacing,
        justification and letter-spacing. This fixes the first two issues and
        allows us to render Scribd's HTML5 documents much better.

        Test: fast/text/atsui-spacing-features.html

        * platform/graphics/chromium/FontLinux.cpp:
        (WebCore::TextRunWalker::TextRunWalker):
        (WebCore::TextRunWalker::setWordSpacingAdjustment):
        (WebCore::TextRunWalker::setLetterSpacingAdjustment):
        (WebCore::TextRunWalker::setPadding):
        (WebCore::TextRunWalker::setGlyphXPositions):
        (WebCore::TextRunWalker::isCodepointSpace):
        (WebCore::Font::drawComplexText):
        (WebCore::Font::floatWidthForComplexText):
        (WebCore::Font::offsetForPositionForComplexText):
        (WebCore::Font::selectionRectForComplexText):

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@65428 268f45cc-cd09-0410-ab3c-d52691b4dbfc