This patch adds support for CSS gradients as background images.  RenderStyles now hold a StyleImage
        RefPtr, which is a wrapper for two types of images: CachedImages (loaded from URLs) and generated images
        (patterns created on the fly such as gradients).

        All of the features of <canvas> are supported: gradients can be linear or radial, have multiple stops, and
        can specify their points as percentages (for reusable gradients across different box sizes).

        Reviewed by olliej

        Added fast/gradients/simple-gradients.html

        * WebCore.xcodeproj/project.pbxproj:
        * css/CSSBorderImageValue.cpp:
        (WebCore::CSSBorderImageValue::CSSBorderImageValue):
        * css/CSSBorderImageValue.h:
        (WebCore::CSSBorderImageValue::imageValue):
        (WebCore::CSSBorderImageValue::generatorValue):
        * css/CSSComputedStyleDeclaration.cpp:
        (WebCore::CSSComputedStyleDeclaration::getPropertyCSSValue):
        * css/CSSGradientValue.cpp: Added.
        (WebCore::CSSGradientValue::cssText):
        (WebCore::CSSGradientValue::createGradient):
        (WebCore::CSSGradientValue::image):
        (WebCore::compareStops):
        (WebCore::CSSGradientValue::sortStopsIfNeeded):
        (WebCore::CSSGradientValue::resolvePoint):
        (WebCore::CSSGradientValue::resolveRadius):
        * css/CSSGradientValue.h: Added.
        (WebCore::):
        (WebCore::CSSGradientColorStop::CSSGradientColorStop):
        (WebCore::CSSGradientValue::CSSGradientValue):
        (WebCore::CSSGradientValue::type):
        (WebCore::CSSGradientValue::setType):
        (WebCore::CSSGradientValue::setFirstX):
        (WebCore::CSSGradientValue::setFirstY):
        (WebCore::CSSGradientValue::setSecondX):
        (WebCore::CSSGradientValue::setSecondY):
        (WebCore::CSSGradientValue::setFirstRadius):
        (WebCore::CSSGradientValue::setSecondRadius):
        (WebCore::CSSGradientValue::addStop):
        * css/CSSImageGeneratorValue.cpp: Added.
        (WebCore::CSSImageGeneratorValue::~CSSImageGeneratorValue):
        (WebCore::CSSImageGeneratorValue::addClient):
        (WebCore::CSSImageGeneratorValue::removeClient):
        (WebCore::CSSImageGeneratorValue::getImage):
        (WebCore::CSSImageGeneratorValue::putImage):
        * css/CSSImageGeneratorValue.h: Added.
        (WebCore::CSSImageGeneratorValue::isImageGeneratorValue):
        * css/CSSImageValue.h:
        (WebCore::CSSImageValue::isImageValue):
        * css/CSSParser.cpp:
        (WebCore::CSSParser::parseBackgroundImage):
        (WebCore::BorderImageParseContext::commitImage):
        (WebCore::CSSParser::parseBorderImage):
        (WebCore::parseGradientPoint):
        (WebCore::parseGradientColorStop):
        (WebCore::CSSParser::parseGradient):
        * css/CSSParser.h:
        * css/CSSStyleSelector.cpp:
        (WebCore::CSSStyleSelector::applyProperty):
        (WebCore::CSSStyleSelector::createStyleImage):
        (WebCore::CSSStyleSelector::mapBackgroundImage):
        * css/CSSStyleSelector.h:
        * css/CSSValue.h:
        (WebCore::CSSValue::isImageValue):
        (WebCore::CSSValue::isImageGeneratorValue):
        * html/CanvasRenderingContext2D.cpp:
        (WebCore::CanvasRenderingContext2D::isPointInPath):
        * platform/graphics/BitmapImage.cpp:
        (WebCore::BitmapImage::BitmapImage):
        (WebCore::BitmapImage::dataChanged):
        (WebCore::BitmapImage::frameCount):
        * platform/graphics/BitmapImage.h:
        * platform/graphics/GraphicsContext.cpp:
        (WebCore::GraphicsContext::clipToImageBuffer):
        * platform/graphics/GraphicsContext.h:
        * platform/graphics/ImageBuffer.h:
        (WebCore::ImageBuffer::cgImage):
        (WebCore::ImageBuffer::image):
        * platform/graphics/cg/GraphicsContextCG.cpp:
        (WebCore::GraphicsContext::clipToImageBuffer):
        (WebCore::GraphicsContext::paintBuffer):
        (WebCore::GraphicsContext::drawImage):
        * platform/graphics/cg/ImageBufferCG.cpp:
        (WebCore::ImageBuffer::create):
        (WebCore::ImageBuffer::ImageBuffer):
        (WebCore::ImageBuffer::~ImageBuffer):
        (WebCore::ImageBuffer::image):
        (WebCore::ImageBuffer::getImageData):
        (WebCore::ImageBuffer::putImageData):
        (WebCore::ImageBuffer::toDataURL):
        * platform/graphics/cg/ImageCG.cpp:
        (WebCore::BitmapImage::BitmapImage):
        (WebCore::BitmapImage::draw):
        (WebCore::Image::drawPattern):
        * platform/graphics/qt/ImageQt.cpp:
        (WebCore::BitmapImage::BitmapImage):
        * rendering/InlineFlowBox.cpp:
        (WebCore::InlineFlowBox::paintBackground):
        * rendering/RenderBox.cpp:
        (WebCore::RenderBox::calculateBackgroundSize):
        (WebCore::RenderBox::imageChanged):
        (WebCore::RenderBox::paintBackgroundExtended):
        * rendering/RenderObject.cpp:
        (WebCore::RenderObject::mustRepaintBackgroundOrBorder):
        (WebCore::RenderObject::updateBackgroundImages):
        (WebCore::RenderObject::arenaDelete):
        * rendering/RenderStyle.cpp:
        (WebCore::StyleCachedImage::cssValue):
        (WebCore::StyleCachedImage::canRender):
        (WebCore::StyleCachedImage::imageSize):
        (WebCore::StyleCachedImage::setImageContainerSize):
        (WebCore::StyleCachedImage::addClient):
        (WebCore::StyleCachedImage::removeClient):
        (WebCore::StyleCachedImage::image):
        (WebCore::StyleGeneratedImage::cssValue):
        (WebCore::StyleGeneratedImage::imageSize):
        (WebCore::StyleGeneratedImage::setImageContainerSize):
        (WebCore::StyleGeneratedImage::addClient):
        (WebCore::StyleGeneratedImage::removeClient):
        (WebCore::StyleGeneratedImage::image):
        * rendering/RenderStyle.h:
        (WebCore::StyleImage::StyleImage):
        (WebCore::StyleImage::~StyleImage):
        (WebCore::StyleImage::operator==):
        (WebCore::StyleImage::canRender):
        (WebCore::StyleImage::isCachedImage):
        (WebCore::StyleImage::isGeneratedImage):
        (WebCore::StyleCachedImage::StyleCachedImage):
        (WebCore::StyleCachedImage::data):
        (WebCore::StyleCachedImage::isCachedImage):
        (WebCore::StyleGeneratedImage::StyleGeneratedImage):
        (WebCore::StyleGeneratedImage::data):
        (WebCore::StyleGeneratedImage::isGeneratedImage):
        (WebCore::BackgroundLayer::backgroundImage):
        (WebCore::BackgroundLayer::setBackgroundImage):
        (WebCore::BackgroundLayer::containsImage):
        (WebCore::RenderStyle::backgroundImage):
        (WebCore::RenderStyle::initialBackgroundImage):
        * svg/graphics/cg/SVGPaintServerGradientCg.cpp:
        (WebCore::SVGPaintServerGradient::teardown):
        * svg/graphics/cg/SVGResourceMaskerCg.mm:
        (WebCore::SVGResourceMasker::applyMask):



git-svn-id: http://svn.webkit.org/repository/webkit/trunk@31830 268f45cc-cd09-0410-ab3c-d52691b4dbfc