Reviewed by Tony Chang.

        [chromium] refactor complex text on Linux
        https://bugs.webkit.org/show_bug.cgi?id=51956

        Pull out TextRunWalker from FontLinux.cpp.  Put it in its own file.
        Rename it to ComplexTextController, to match platform/graphics/mac
        more closely.

        No tests because the change is just renaming a class.

        * WebCore.gyp/WebCore.gyp:
        * platform/graphics/chromium/ComplexTextControllerLinux.cpp: Added.
        (WebCore::ComplexTextController::ComplexTextController):
        (WebCore::ComplexTextController::~ComplexTextController):
        (WebCore::ComplexTextController::isWordBreak):
        (WebCore::ComplexTextController::determineWordBreakSpacing):
        (WebCore::ComplexTextController::setPadding):
        (WebCore::ComplexTextController::reset):
        (WebCore::ComplexTextController::setBackwardsIteration):
        (WebCore::ComplexTextController::nextScriptRun):
        (WebCore::ComplexTextController::widthOfFullRun):
        (WebCore::ComplexTextController::setupFontForScriptRun):
        (WebCore::ComplexTextController::allocHarfbuzzFont):
        (WebCore::ComplexTextController::deleteGlyphArrays):
        (WebCore::ComplexTextController::createGlyphArrays):
        (WebCore::ComplexTextController::resetGlyphArrays):
        (WebCore::ComplexTextController::shapeGlyphs):
        (WebCore::ComplexTextController::setGlyphXPositions):
        (WebCore::ComplexTextController::normalizeSpacesAndMirrorChars):
        (WebCore::ComplexTextController::getNormalizedTextRun):
        * platform/graphics/chromium/ComplexTextControllerLinux.h: Added.
        (WebCore::ComplexTextController::setWordSpacingAdjustment):
        (WebCore::ComplexTextController::setLetterSpacingAdjustment):
        (WebCore::ComplexTextController::letterSpacing):
        (WebCore::ComplexTextController::setXOffsetToZero):
        (WebCore::ComplexTextController::rtl):
        (WebCore::ComplexTextController::glyphs):
        (WebCore::ComplexTextController::length):
        (WebCore::ComplexTextController::xPositions):
        (WebCore::ComplexTextController::advances):
        (WebCore::ComplexTextController::width):
        (WebCore::ComplexTextController::logClusters):
        (WebCore::ComplexTextController::numCodePoints):
        (WebCore::ComplexTextController::fontPlatformDataForScriptRun):
        (WebCore::ComplexTextController::isCodepointSpace):
        * platform/graphics/chromium/FontLinux.cpp:
        (WebCore::Font::drawComplexText):
        (WebCore::Font::floatWidthForComplexText):
        (WebCore::glyphIndexForXPositionInScriptRun):
        (WebCore::Font::offsetForPositionForComplexText):
        (WebCore::Font::selectionRectForComplexText):

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@75108 268f45cc-cd09-0410-ab3c-d52691b4dbfc