Reviewed by Dan Bernstein.

        Adding tests for canvas compositing modes to make sure the results don't change after:
        <rdar://problem/5640059> GraphicsContext::setCompositeOperation should use CGContextSetBlendMode

        The following compositing modes don't pass however that is covered by another bug:
        source-in
        source-out
        destination-in
        destination-atop
        copy
        <rdar://problem/5651783> Some canvas tag compositing modes don't render correctly

        * fast/canvas/canvas-composite.html: Added.
        * platform/mac/fast/canvas/canvas-composite-expected.checksum: Added.
        * platform/mac/fast/canvas/canvas-composite-expected.png: Added.
        * platform/mac/fast/canvas/canvas-composite-expected.txt: Added.

WebCore:

        Reviewed by Dan Bernstein.

        Test: fast/canvas/canvas-composite.html

        Fix for:
        <rdar://problem/5640059> GraphicsContext::setCompositeOperation should use CGContextSetBlendMode

        This fix makes setCompositeOperation consistent across all platforms that use CG.

        The following compositing modes don't pass however that is covered by another bug:
        source-in
        source-out
        destination-in
        destination-atop
        copy
        <rdar://problem/5651783> Some canvas tag compositing modes don't render correctly

        * platform/graphics/GraphicsTypes.h:
        * platform/graphics/cg/GraphicsContextCG.cpp:
        (WebCore::GraphicsContext::setCompositeOperation):
        * platform/graphics/mac/GraphicsContextMac.mm:
        * platform/win/GraphicsContextWin.cpp:



git-svn-id: http://svn.webkit.org/repository/webkit/trunk@28874 268f45cc-cd09-0410-ab3c-d52691b4dbfc