Introduce SVGLengthContext, to allow to resolve relative units to arbitary viewports
        https://bugs.webkit.org/show_bug.cgi?id=71780

        Reviewed by Zoltan Herczeg.

        Introduce SVGLengthContext to cleanup SVGLength, by moving all conversion of relative units that depend on style or viewport
        out of SVGLength, into SVGLengthContext. Pass SVGLengthContext& to SVGLength::value/setValue/... functions instead of a pure
        "const SVGElement* context", which was previously used to determine the viewport when resolving percentage units.
        SVGLengthContext carries an additional FloatRect of the custom viewport, to which percentages are resolved, if specified.

        This allows us to kill several duplicates of the same code, which handles objectBoundingBox mode for gradients/patterns/masks/etc..
        A follow-up patch will convert filters to use the new SVGLengthContext::resolveRectangle code as well.

        This is a preparation for bug 10430, to fix feImage + objectBoundingBox support when rendering referenced elements, instead of files.

        Doesn't affect any tests yet.

        * CMakeLists.txt:
        * GNUmakefile.list.am:
        * Target.pri:
        * WebCore.gypi:
        * WebCore.vcproj/WebCore.vcproj:
        * WebCore.xcodeproj/project.pbxproj:
        * rendering/svg/RenderSVGResourceGradient.cpp:
        (WebCore::RenderSVGResourceGradient::applyResource):
        * rendering/svg/RenderSVGResourceGradient.h:
        * rendering/svg/RenderSVGResourceLinearGradient.h:
        (WebCore::RenderSVGResourceLinearGradient::gradientUnits):
        * rendering/svg/RenderSVGResourcePattern.cpp:
        (WebCore::RenderSVGResourcePattern::applyResource):
        (WebCore::calculatePatternBoundaries):
        (WebCore::RenderSVGResourcePattern::buildTileImageTransform):
        (WebCore::RenderSVGResourcePattern::createTileImage):
        * rendering/svg/RenderSVGResourceRadialGradient.h:
        (WebCore::RenderSVGResourceRadialGradient::gradientUnits):
        * rendering/svg/SVGRenderTreeAsText.cpp:
        (WebCore::writeCommonGradientProperties):
        (WebCore::writeSVGResourceContainer):
        * svg/GradientAttributes.h:
        (WebCore::GradientAttributes::GradientAttributes):
        (WebCore::GradientAttributes::gradientUnits):
        (WebCore::GradientAttributes::setGradientUnits):
        (WebCore::GradientAttributes::hasGradientUnits):
        * svg/PatternAttributes.h:
        (WebCore::PatternAttributes::PatternAttributes):
        (WebCore::PatternAttributes::patternUnits):
        (WebCore::PatternAttributes::patternContentUnits):
        (WebCore::PatternAttributes::setPatternUnits):
        (WebCore::PatternAttributes::setPatternContentUnits):
        (WebCore::PatternAttributes::hasPatternUnits):
        (WebCore::PatternAttributes::hasPatternContentUnits):
        * svg/SVGAllInOne.cpp:
        * svg/SVGElement.h:
        (WebCore::SVGElement::operator SVGLengthContext):
        * svg/SVGFilterElement.cpp:
        (WebCore::SVGFilterElement::filterBoundingBox):
        * svg/SVGLength.cpp:
        (WebCore::SVGLength::SVGLength):
        (WebCore::SVGLength::unitMode):
        (WebCore::SVGLength::value):
        (WebCore::SVGLength::setValue):
        (WebCore::SVGLength::convertToSpecifiedUnits):
        * svg/SVGLength.h:
        (WebCore::SVGLength::blend):
        * svg/SVGLengthContext.cpp: Added.
        (WebCore::SVGLengthContext::SVGLengthContext):
        (WebCore::SVGLengthContext::resolveRectangle):
        (WebCore::SVGLengthContext::resolvePoint):
        (WebCore::SVGLengthContext::resolveLength):
        (WebCore::SVGLengthContext::convertValueToUserUnits):
        (WebCore::SVGLengthContext::convertValueFromUserUnits):
        (WebCore::SVGLengthContext::convertValueFromUserUnitsToPercentage):
        (WebCore::SVGLengthContext::convertValueFromPercentageToUserUnits):
        (WebCore::SVGLengthContext::convertValueFromUserUnitsToEMS):
        (WebCore::SVGLengthContext::convertValueFromEMSToUserUnits):
        (WebCore::SVGLengthContext::convertValueFromUserUnitsToEXS):
        (WebCore::SVGLengthContext::convertValueFromEXSToUserUnits):
        (WebCore::SVGLengthContext::determineViewport):
        * svg/SVGLengthContext.h: Added.
        (WebCore::SVGLengthContext::resolveRectangle):
        * svg/SVGLinearGradientElement.cpp:
        (WebCore::SVGLinearGradientElement::collectGradientAttributes):
        (WebCore::SVGLinearGradientElement::calculateStartEndPoints):
        * svg/SVGMaskElement.cpp:
        (WebCore::SVGMaskElement::maskBoundingBox):
        * svg/SVGPatternElement.cpp:
        (WebCore::SVGPatternElement::collectPatternAttributes):
        * svg/SVGRadialGradientElement.cpp:
        (WebCore::SVGRadialGradientElement::collectGradientAttributes):
        (WebCore::SVGRadialGradientElement::calculateFocalCenterPointsAndRadius):


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@99561 268f45cc-cd09-0410-ab3c-d52691b4dbfc