Reviewed by Eric Seidel.

        https://bugs.webkit.org/show_bug.cgi?id=25709 part nine
        Factor Cairo-specific implementation out of ImageDecoder.h into
        ImageDecoderCairo.cpp.  Add some comments to functions declared
        in ImageDecoder.h.

        * GNUmakefile.am:
        * WebCore.vcproj/WebCore.vcproj:
        * platform/image-decoders/ImageDecoder.h:
        * platform/image-decoders/cairo: Added.
        * platform/image-decoders/cairo/ImageDecoderCairo.cpp: Added.
        (WebCore::RGBA32Buffer::RGBA32Buffer):
        (WebCore::RGBA32Buffer::clear):
        (WebCore::RGBA32Buffer::zeroFill):
        (WebCore::RGBA32Buffer::copyBitmapData):
        (WebCore::RGBA32Buffer::setSize):
        (WebCore::RGBA32Buffer::asNewNativeImage):
        (WebCore::RGBA32Buffer::hasAlpha):
        (WebCore::RGBA32Buffer::setHasAlpha):
        (WebCore::RGBA32Buffer::operator=):
        (WebCore::RGBA32Buffer::width):
        (WebCore::RGBA32Buffer::height):
        (WebCore::RGBA32Buffer::getAddr):



git-svn-id: http://svn.webkit.org/repository/webkit/trunk@44652 268f45cc-cd09-0410-ab3c-d52691b4dbfc