Reviewed by Darin Fisher.

        [chromium] Accelerated Compositing: screen garbage when scrolling
        https://bugs.webkit.org/show_bug.cgi?id=45092

        Split LayerRenderChromium::drawLayers into several different
        functions, responsible for preparing the backbuffer, updating the
        root texture, compositing and performing the final
        swapbuffers. This are then used by the new
        WebViewImpl::composite rendering path.

        * platform/graphics/chromium/LayerChromium.cpp:
        (WebCore::LayerChromium::setBounds):
        (WebCore::LayerChromium::setFrame):
        (WebCore::LayerChromium::setNeedsDisplay):
        (WebCore::LayerChromium::resetNeedsDisplay):
        * platform/graphics/chromium/LayerChromium.h:
        (WebCore::LayerChromium::dirtyRect):
        * platform/graphics/chromium/LayerRendererChromium.cpp:
        (WebCore::LayerRendererChromium::prepareToDrawLayers):
        (WebCore::LayerRendererChromium::updateRootLayerTextureRect):
        (WebCore::LayerRendererChromium::drawLayers):
        (WebCore::LayerRendererChromium::present):
        * platform/graphics/chromium/LayerRendererChromium.h:



git-svn-id: http://svn.webkit.org/repository/webkit/trunk@67244 268f45cc-cd09-0410-ab3c-d52691b4dbfc