Improve the performance of the GUIMark benchmark by 2x in the CoreGraphics code path.

        Whenever a foreground image changes size rapidly, we will now dynamically shift into rendering it
        using low quality scaling.  Once the animation completes, the image will repaint at high quality.
        Scaled images will still render at high quality by default, only shifting into low quality if
        the scale factor is rapidly changing.  This change raises GUIMark from 21fps to 34fps on my machine.

        Rewrite the Image draw method to avoid the use of throwaway CG subimages.  Instead the entire image is
        always drawn (with the appropriate clip and scale set up to make sure the correct subimage portion shows up
        in the destination rect).  This change raises GUIMark from 34fps to 43fps on my machine.

        Reviewed by Darin

        * platform/graphics/GraphicsContext.cpp:
        (WebCore::GraphicsContext::drawImage):
        * platform/graphics/cg/ImageCG.cpp:
        (WebCore::BitmapImage::draw):
        * rendering/RenderImage.cpp:
        (WebCore::RenderImageScaleData::RenderImageScaleData):
        (WebCore::RenderImageScaleData::~RenderImageScaleData):
        (WebCore::RenderImageScaleData::size):
        (WebCore::RenderImageScaleData::time):
        (WebCore::RenderImageScaleData::useLowQualityScale):
        (WebCore::RenderImageScaleData::hiqhQualityRepaintTimer):
        (WebCore::RenderImageScaleData::setSize):
        (WebCore::RenderImageScaleData::setTime):
        (WebCore::RenderImageScaleData::setUseLowQualityScale):
        (WebCore::RenderImageScaleObserver::shouldImagePaintAtLowQuality):
        (WebCore::RenderImageScaleObserver::imageDestroyed):
        (WebCore::RenderImageScaleObserver::highQualityRepaintTimerFired):
        (WebCore::RenderImage::highQualityRepaintTimerFired):
        (WebCore::RenderImage::~RenderImage):
        (WebCore::RenderImage::paintReplaced):
        * rendering/RenderImage.h:



git-svn-id: http://svn.webkit.org/repository/webkit/trunk@34210 268f45cc-cd09-0410-ab3c-d52691b4dbfc